Linzey - Vertebrate Biology - Chapter 14 pps

Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 CHAPTER 14 Techniques for Ecological and Behavioral Studies ■ INTRODUCTION Discovery and problem solving in all fields of science employ techniques of gathering, coordinating, organizing, and evalu- ating information as it relates to a specific subject. In a scientific approach to any problem, the researcher must first ask a question or identify a problem based on observations of objects or events. Then, a hypothesis or potential answer to the question being asked is proposed, and the investigator predicts what the consequences might be if the hypothesis is valid. The investigator then devises ways to test the hypothesis by making observations, developing models, or performing experiments. Hypotheses must be testable; those that are not testable are inadmissible in science. Observations and/or tests should be repeated as often as necessary to determine whether results will be consistent and as predicted. Hypotheses that are found upon testing to be contradicted by the evidence must be modified or abandoned. The investigator must then report objectively on the results and on conclusions drawn from them, presenting both the data and the investigator’s intepretation of the information as it relates to the hypothesis. This mode of action is known as the scientific method. Critical evaluation of the techniques—or methodology—used in any scientific investigation is extremely important. Thus, scientists constantly must be con- cerned with the selection and application of the best techniques for use in each of these steps. A deficiency in any of these steps will hinder the interpretation of the results. Limitations inherent in field and laboratory investigations of animal populations make it even more critical that researchers choose most carefully the techniques to be used. The mobility, secretiveness, and constant fluctuation in numbers of practically all wild animals make precise data difficult to secure. For these reasons, census work often requires a major portion of the time in many field investigations. The secretive nature of most wild animals makes the determination of the influence of pathology, disease, and related factors especially difficult to examine for any species of animal in nature. Because the objective of any investigation is to gather and evaluate accurate data, the investigator must always bear in mind that the techniques used should yield data that are objective and reliable. If the investigator’s approach to the problem is not scientifically sound—if the techniques are inadequate or flawed—the results will be of little value. Critical appraisal of the investigational techniques should be made at the begin- ning, not at the termination, of the research project. The difficulties mentioned above highlight the need for careful planning and equally careful collection of data on the part of fish and wildlife investigators. Inexperienced investigators often propose to collect data that, due to field conditions or the characteristics of the animal being investigated, are impossible to secure. Thus, detailed planning, including critical scrutiny of all the proposed techniques to be employed, is necessary to ensure that insurmountable problems are not encountered in the proposed study. Long-term studies are needed to learn these limitations and to collect the necessary information; yet this is rarely accomplished, since most studies are short-term (and are financed as short-term projects). Many studies do not require the capture of individual animals. Techniques employing simple observation, aerial photography, aerial censusing, transect counts, actual counting of individuals such as fishes and hawks that pass a certain point on their migratory journeys, and identification of signs such as tracks and scats can provide valuable data. For some purposes, animals such as amphibians, reptiles, and mammals killed by vehicles (DOR=dead on road) can yield useful data. Many behavioral studies can be done in the animal’s natural habitat. Other studies, however, do require direct contact between animal and investigator. Such studies include those dealing with the collection of anatomical data such as weight, length, condition of molt, or the like; or those dealing with age determination, sex ratios, genetic analyses, home ranges, and parasites. ■ CAPTURE TECHNIQUES A wide variety of techniques are used for capturing vertebrates. Humane capture techniques should always be employed. They should not injure or increase the mortality Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 Techniques for Ecological and Behavioral Studies 391 (a) The cannon net is an effective way of taking gamebirds, unharmed, for scientific purposes. The birds are prebaited at the site; the net is then carefully folded and camouflaged in front of the “cannons.” (b) When properly deployed, the net is highly effective. The birds are snow geese (Chen hyperborea). FIGURE 14.1 (a) (b) of the animals, and they should not cause more than minimal disruption to the animals’ normal behavior patterns. Dip-netting, seining, the use of trap- and gill-nets, and the use of immobilizing chemicals and electroshocking are among the capture methods utilized by fish biologists. Most amphibians can be captured either by hand or with the use of a net. Some terrestrial reptiles also can be taken by hand, although nets, nooses, and tongs frequently are used for some species. Aquatic turtles may be secured through the use of turtle traps, commercial fish trap-nets, and trawls. Nestling birds can be removed from the nest by hand for weighing, sexing, and tagging. Fine-mesh mist nets are often used to capture small flying birds, which become entangled in the mesh and can be removed uninjured for study. Live traps placed on the ground and baited with seeds are used successfully for some granivorous species. The projection, or cannon, net trap is widely used for turkeys and waterfowl (Fig. 14.1). It consists of a large, light net that is carried over the baited birds by mortar projectiles or rockets. Funnel-entrance traps are used commonly for waterfowl. Hawks can be trapped by using traps baited with live prey. Some carrion-eating species have been immobilized by consuming drug-laden meat. Many small-mammal researchers employ traps. These should be live traps suitable for the species, although snap traps were extensively used in the past. Traps may be placed on the surface of the ground or in tunnels, or they may be affixed to the branches of trees. Shrews are taken most effectively in pitfall traps in which a series of containers (cans, plastic cups, etc.) are buried with their tops flush with the ground and loosely covered by a piece of wood or some other object. Due to the shrews’ high metabolism, this method of collection will yield live shrews only if the cans are checked several times each day. If the cans cannot be checked frequently, they can be partially filled with a preservative liquid/fixative to kill and preserve animals for future study. All cans should be removed and the holes filled at the conclusion of the study. Small-mammal distribution studies can be augmented by examining discarded bottles along roadsides. Shrews are the most abundant small mammals found in bottles (Morris and Harper, 1965; Glegg, 1966; Pagels and French, 1987). Examination of owl pellets also can yield valuable distributional and population data on shrews, voles, and other small mammals. Bats usually are captured with mist nets positioned at cave entrances or along watercourse flyways. Nets must be monitored continually, and bats removed as soon as possible in order to prevent injury. Although mammals as large as bears can be trapped successfully with snares and culvert traps, most large mammals are shot with a tranquilizer-containing dart. Fairly accurate estimation of weights of animals in the field must be made for proper dosages to be administered. Drift fences and traps are used for studies on a wide range of terrestrial vertebrates, including amphibians, reptiles, and mammals. This method requires the erection of one or more fences with openings at periodic intervals. The object is to direct the movement of an animal into a trap at one of the openings. ■ IDENTIFICATION TECHNIQUES To study the movements and behavior of animals in the wild, there must be a means of identifying specific individuals. In some cases, this can be accomplished by noting unique individual characteristics such as distinctive coloration, scars, deformities, injuries, or some aberrant behavior. For example, Schaller (1963) found that the noses of mountain goril- las appeared distinctive and served as the best single character for recognizing individuals. In most cases, however, it is not possible to distinguish individuals visually. Therefore, some appropriate method of marking or tagging each individual animal must be devised. In deciding on a particular technique, consideration must be given as to whether the study in question is short-term or long-term and how many animals will be involved. The method selected should not injure the animal, alter the animal’s behavior or locomotion, or cause increased susceptibility to predation. Many identifying techniques have been devised including marking, tagging, photography, use of radio transmitters, and satellite tracking. Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 392 Chapter Fourteen A biologist tags a hawksbill turtle (Eretmochelys imbricata) in an effort to gather more information on the species’ movements and habitat needs. The threats facing this species include habitat destruction and commercial demand for stuffed juveniles and products made out of its shell. FIGURE 14.2 Marking Marking usually refers to changing a part of the animal’s body so that it can be discerned readily from all other members of the population. Moyle and Cech (1996) summarized fish marking methods as follows: “Marks may consist of clipped fin rays, liquid nitrogen ‘cold brands,’ pigmented epidermis from high-pressure spray painting, or fluorescent rings on bones or scales (visible under ultraviolet light) from incor- poration of tetracycline or 2, 4-bis(N, N′-dicarboxymethyl- aminomethyl) fluorescein (DCAF) in the diet.” Juvenile salmonids have been marked chemically by feeding them dissolved strontium, a biologically rare element, which is then incorportated into their scales (Snyder et al., 1992). Amphibians usually are marked by toe clipping—that is, excising the terminal phalanx of one or more toes in a specific pattern. They also may be marked by branding and by the use of dyes and phosphorescent powders. Larval (tadpole) stages may be semipermanently marked by injecting an acrylic polymer dye into the fin. A detailed discussion of marking and tagging techniques suitable for amphibians may be found in Heyer et al. (1994). Lizards and snakes may be marked by toe clipping, by excising specific scales in a prearranged manner, or by using a latex-based house paint. Marking methods for reptiles have been reviewed by Dunham et al. (1988). Individual turtles can be identified by having an identifying mark painted on their shells or by notching specific marginal scutes. Birds may be marked by dyeing their feathers. Mammals may be marked by toe clipping, fur clipping, ear notching, tattooing, branding, dyeing, painting, or bleaching. In the case of toe clipping, smoked paper affixed to plywood or cardboard can be placed throughout the study area so that whenever a marked animal crosses the surface, it will leave its own distinctive identifying imprint. Commercial dyes have been employed in various ways to identify mammals. In some species, the dye is applied to the captured animal prior to its release. In other studies, a marking device may be placed in the animal’s normal habitat (designed in such a way that the animal triggers the device in its typical pattern of activity). Once triggered, the device discharges a quantity of the dye onto the animal’s body. The use of a dye in this manner will provide visual identification until the animal undergoes its next molt. Fluorescent powders have also been used successfully. Tagging Tagging requires the attachment of a metal, plastic, or cloth device to the body of an animal to allow for future identification (Fig. 14.2). Any tagging device must anticipate the growth of the animal and must not impede its movements or other normal behavior. Tagging of fishes can be done by externally and internally attached disks, microtags, dart tags, plates, streamers, and small, implantable metal rods detectable in a magnetic field (Moyle and Cech, 1996). Electronic tags that record depth, water temperature, and light intensity weigh as little as 16 g and can store more than 500,000 data samples (Metcalfe and Arnold, 1997). Data on plaice (Pleuronectes platessa) have been recorded continuously by electronic tags for over 200 days. Amphibian studies have used tags and radioactive isotopes for identifying individual animals. The use of isotopes allows the continuous monitoring of an individual without recapture. Passive integrated transponder (PIT) tags are small, glass-encapsulated diodes (0.1 g) and do not require batteries (Camper and Dixon, 1988). When activated by a detector, they transmit a unique code back to the receiver. PIT tags must be implanted in the animal (thus, infection is a major consideration), and current transponder systems have a very short range. Ingested radio transmitters also have been successful in yielding short-term data on amphibians such as the common frog (Rana temporaria) and the common toad (Bufo bufo) (Oldham and Swan, 1992) as well as on snakes. Several unique methods of tracking turtles have been employed. Stickel’s (1950) attachment of a spool of thread to the carapace of a box turtle yielded valuable data on the movements of this species. The attachment of helium-filled weather balloons to marine turtles allowed tracking of their movements for short periods of time. For years, ornithologists have been studying migration in birds, as well as many other aspects of avian biology, by using aluminum, stainless, or monel alloy leg bands (Figs. 14.3a, b and 14.4). These tags are numbered and contain the address of an agency to which the finder should mail them. In the United States, the agency is the U.S. Fish and Wildlife Ser- vice. Bands come in a variety of sizes, and future growth in the diameter of the leg must be carefully anticipated prior to attachment of the band. These bands have provided valuable data on the migratory habits of many species of birds, but a bird must either be recaptured or found dead in order to be Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 Techniques for Ecological and Behavioral Studies 393 positively identified. A toll-free telephone number (1-800- 327-BAND) is now available to report any bird band identified or recovered in North America. This recording service, developed in cooperation with the National Biological Sur- vey, the U.S. Fish and Wildlife Service, and the Canadian Wildlife Service, can be called from anywhere in the United States, Canada, and most parts of the Caribbean. Colored leg bands, neck bands, or plastic streamers are used in behavioral or home range studies so that individual birds can be identified without recapture (Fig. 14.5). Patagial tags and feather grafts also have been used as field identification tags (Fig. 14.6). Researchers studying western European populations of the white stork (Ciconia ciconia) implanted electronic PIT tags (30 mm long, 3 mm in diameter, 0.8 g mass) beneath the stork’s skin (Michard et al., 1995). The tag, which permits automatic individual identification, is long-lasting because it does not require a battery. Body condition also can be assessed, as the birds weigh themselves on scales coupled with tag-identification systems at feeding sites. The tags are read by an antenna-recorder from a distance of approximately 1 m. Mammals may be tagged in a variety of ways. Studies involving bats utilize lightweight aluminum bands similar to those used for birds. These bands are numbered and are affixed to the forearms of the bats. In some studies, inch-long luminous cyalume rods have been attached to the backs of bats for easier tracking at night. Metal or plastic ear tags FIGURE 14.3 (a) (b) (a) Banding a woodcock (Philohela minor). Future growth of the leg must be anticipated when selecting the proper size band. (b) Bands of various sizes, made of soft, lightweight metal, are provided by the U.S. Fish and Wildlife Service for bird banding to determine the migratory movements of various species. FIGURE 14.4 The neck collars on these parent Canada geese (Branta canadensisi) make it possible to keep track of eggs and young up to the migratory stage, yielding information on daily and seasonal habitat preferences. Colored patagial tags have been used to study the breeding behavior of mourning doves (Zenaidura macroura). FIGURE 14.5 have been used on mammals of all sizes. In some cases, colored plastic streamers have been attached to the tags so that visual identification can be made at a distance. Neck collars are used on larger mammals. Unfortunately, all tags are Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 394 Chapter Fourteen Feather graft of an immature wing feather onto the head of a great black-backed gull (Larus marinus). Best results are obtained when the graft is made on immature birds. The grafted feather is permanent and molts with other body feathers, thereby serving as a permanent field identification “tag.” FIGURE 14.6 subject to loss; Siniff and Ralls (1991), for example, reported an estimated annual tag loss rate of 26 percent in California sea otters (Enhydra lutris). Spool-and-line tracking has been employed in several mammal studies. This technique utilizes a spool of thread attached to the animal’s body. The spool continuously releases thread as the animal moves, thus providing a fairly accurate representation of the animal’s travels. For example, Hawkins and Macdonald (1992) used spools attached to webbed collars to investigate the movements of badgers (Meles meles). One disadvantage of this method is that it yields only 1 or 2 nights of potentially high-quality data per capture. Dyes have been incorporated in food in order to stain the feces. In small-mammal studies, dropping boards are placed throughout the study area in order to facilitate the recovery of dyed fecal pellets. This is a temporary technique that depends on the rate of passage of the food material through the animal’s alimentary canal. Radioactive isotopes in the form of wires and pellets have been inserted under the skin of various species of mammals. This method of tagging permits continuous location of the animal with minimal disturbance. Radioactive materials injected into animals will render their feces identifiable. The use of genetic tagging has revealed individual local and migratory movements and yielded estimations of abundance in humpback whales (Megaptera novaeangliae) (Palsboll et al., 1997). Genetic tagging consists of collecting skin samples, removing the DNA, and determining the sex and geno- type at six Mendelian-inherited microsatellite loci for each sample. More than 2,300 unique genotypes were identified. Genetic tracking has also allowed the tracking of an individual whale from fishery to market (Cipriano and Palumbi, 1999). This technique, as well as similar genetic tools, will allow new management efforts to focus on the individual, rather than the species, and to distinguish individual “legal” whales (those of a particular sex and size which can be legally harvested) from all others. Tagging frequently requires specific federal and/or state permits, as well as approval from university and institutional animal care and/or ethics committees in many instances, particularly when dealing with species whose travels cross international boundaries, such as most birds. Researchers must be qualified in identification and handling of particular species, as well as in the tagging/marking techniques to be employed. Photography Photography is useful for making a permanent record of the location and/or behavior of a marked or tagged animal. Approximately 80 percent of the manatees (Trichechus man- atus) in the Homosassa and Crystal rivers in Florida are dis- tinctively scarred, primarily from boat strikes. These scar patterns have been used to identify individual manatees. Pho- tographs were taken at regular intervals (twice a week, weekly, biweekly), both from the water’s surface and from beneath the surface, and were incorporated into an identification cat- alogue (Powell and Rathbun, 1984; Rathbun et al., 1990). Resightings of humpback whales (Megaptera novaeangliae) returning to their summer feeding grounds have been veri- fied photographically. Photoidentification of cetaceans is a worldwide ongoing endeavor with regional catalogues and specific repositories of all photographed whales. Photography also has been used in some studies so that an unsuspecting animal triggers a mechanism and takes its own picture. This not only provides a record of the animal’s presence but may also identify food brought to the nest and the frequency and length of absence from the nest. A clock or timing device can be positioned so that it is included in the photograph and records the time the photograph was taken. Small video systems and data loggers that were mounted on the heads of four adult Weddell seals (Leptonychotes weddellii) at McMurdo Sound in Antarctica have revealed some aspects of the secret lives of diving animals (Davis et al., 1999) (Fig. 14.7). The video system recorded images of the seal’s head and the environment immediately in front of the animal. Filming was accomplished in near-infrared light emitted from the camera like a flashlight. The light, which was invisible to the seal’s eye and its prey, should not have altered either one’s behavior. The data logger recorded time, depth, water speed, and compass bearing once per second. Flipper stroke frequency and ambient sound were recorded continuously on the audio channels. Several unknown tactics used by the seals to extract prey from their refuges in the ice were revealed. Radio Transmitters One of the earliest reports on the use of radio telemetry to locate free-ranging animals was their use on woodchucks (Marmota monax) by LeMunyan (1959). The use of radio transmitters has met with considerable success since that Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 Techniques for Ecological and Behavioral Studies 395 A Weddell seal (Leptonychotes weddellii) surfaces in McMurdo Sound, Antarctica, with a 40-pound cod in its mouth and a video camera strapped to its head. Filming was accomplished in near-infrared light emitted from the camera. The video camera and data logger revealed heretofore unknown behavior and tactics used by the seals to secure their food beneath the ice. FIGURE 14.7 time, as transmitters continue to be miniaturized and receiv- ing equipment continues to be improved. In many ways, the use of radio transmitters has revolutionized the study of animal movements. They have been used in studies involving all of the vertebrate groups. The use of radio telemetry in field studies of vertebrates provides the ability to locate the transmitter regularly, both day and night, to check on the location and condition of the carrier. Radio telemetry is valuable in studying predation, individual behavior patterns, and home ranges. Several telemetry techniques have been designed specifically for detecting mortality in free-ranging animals. For example, transmitters may contain temperature sensors that detect the drop in body temperature upon the death of the animal. Transmitters may be strapped to the body, attached by means of a collar placed around the neck (Fig. 14.8), wired to the carapace of turtles, or implanted intraperitoneally or subcutaneously (Ralls et al., 1989; Werner, 1991; Rowe and Moll, 1991; and others). For example, surgically implanted temperature-sensitive radio transmitters revealed daily variations in the body temperatures of free-ranging garter snakes (Thamnophis elegans vagrans) in eastern Washington (Peter- son, 1987) (Fig. 14.9). Collars may be designed to deterio- rate after a certain length of time, or in long-term studies, the animal may need to be recaptured and refitted with a new collar. Intraperitoneal radio transmitter implants were found to have no effect on reproductive performance (copu- lation, embryonic and fetal development, and lactation) in river otters (Reid et al., 1986). Transmitters have been glued to the bony shells of some species of turtles, but the oily, flexible skin that covers the thin, loosely fused, bony plates in a leatherback sea turtle’s carapace resists adhesives. In an experimental technique, the bone is pierced with half-inch-long screws made of a syn- thetic polymer that slowly dissolves (Raloff, 1998). A nylon suture is threaded through each screw and serves to firmly attach the transmitter. As the screws dissolve, they are replaced by bone that continues to anchor the sutures until they weaken and release the transmitter. Male elk (Cervus elaphus) with a radio transmitter, permitting movement and behavioral studies of animals of known age and sex, even though they may be located several miles away. FIGURE 14.8 Time of day 50 40 30 20 10 0 -10 1800 2400 600 1200 1800 2400 Oscillating pattern Plateau pattern No. 20 4-5 August 1979 No. 30 6-7 April 1980 Smooth pattern No. 135 2-5 September 1979 Daily Variation In Snake Temperatures T b T b T b Temperature ( C) o Surgically implanted temperature-sensitive radio transmitters have been used to reveal daily variations in the body temperatures of free-ranging vertebrates including garter snakes (Thamnophis elegans vagrans) in eastern Washington. The daily body temperature patterns shown here are classified as (a) plateau pattern, (b) smooth pattern, and (c) oscillating pattern. Sunrise (↑) and sunset (↓) are indicated on the time axis. Source: Data from Peterson in Ecology, 68(1)1987. FIGURE 14.9 Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 BIO-NOTE 14.1 Teaching Birds to Migrate Trumpeter swans (Cygnus buccinator) are white with a black beak, weigh up to 13.5 kg, have a 2.5-m wing span, and can stand 1.8 m tall with neck outstretched. They vanished from the Chesapeake Bay nearly 200 years ago. Scientists working with the Defenders of Wildlife, a Washington, D.C.–based conservation organization, and the U.S. Fish and Wildlife Service are now trying to restore America’s largest waterfowl to the mid-Atlantic region by reteaching the birds to migrate by using a bright yellow ultralight plane with an overarching white wing. The goal of this project is to reestablish a migration route between upstate New York and Maryland’s Eastern Shore. Migration is important because birds that do not fly south for the winter are more likely to exhaust their food supply, become a nuisance to people, get sick, or freeze to death. Trumpeter swans learn to migrate from their parents, but if the older birds in a flock are killed by hunters, the young do not know where to migrate and the knowledge is forever lost. In December 1997, three trumpeter swans followed the ultralight plane from the Airlie Environmental Center in Warrenton, Virginia, to open tidewater marshes near Cambridge in Dorchester County, Maryland, a distance of 166 km (Fig. 14.10). All three swans returned halfway from their winter site near Cambridge to Airlie in Spring 1998, not deviating by more than 5 miles from the pre-selected route they had been shown in December 1997. One returned to within 10 miles of Airlie; another was injured and was trucked back. The third was also trucked back from Cambridge after backtracking there. None of these three females returned to their winter site near Cambridge in 1998–99. They remained at Airlie. A second project, begun in December 1998, involved transporting 13 trumpeter swans from where they were trained at a traditional breeding ground at a New York Department of Environmental Conservation site near Buf- falo, to the Wildfowl Trust of North America on Chesa- peake Bay near Grasonville, Maryland. Instead of flying them the entire 320-mile route, they were trucked between stops with the birds being flown as high as possible at each stop. In Spring 1999, this flock, while showing migration intention behavior, did not explore more than 10 miles from their wintering quarters. Thus, having failed to return to New York on their own, they were trucked back in May to the New York Department of Conservation’s Oak Orchard Wildlife Management Area a few miles from where they were trained during Fall 1998. On January 22, 2000, one of the experimental trumpeter swans arrived in Clays- burg, Pennsylvania, roughly 210 miles due south from the summer site and approximately 100 miles west of the migration route. Since the male bird arrived shortly after a storm, researchers feel that it may have been blown off course. In 1993, a motorized ultralight led a Canada goose migration from Ontario, Canada, to the Airlie Center, a trip depicted in the 1996 movie Fly Away Home. In October 1995, an ultralight aircraft led eight sandhill cranes on an 11-day, 1,204-km trip from Idaho to the Bosque del Apache National Wildlife Refuge in New Mexico. In October 1997, an ultralight painted to look like a whooping crane guided two of the endangered white birds and six sandhill cranes on a 9-day flight from Idaho to New Mexico. Lewis, 1996 Rininger, 2000 396 Chapter Fourteen Satellite Tracking Satellite tracking is one of the latest tools in the repertoire of wildlife biologists. It allows for monitoring of an individual by providing an update with every pass of the satellite. It has been used successfully on a variety of species, including sea turtles, penguins, whales, elephant seals, ele- phants, caribou, bears, musk-oxen, and manatees (Mate, 1989; Reynolds, 1989; Rathbun et al., 1990; Holden, 1992; Stewart and DeLong, 1995; Reid, 1997). One of the first successful tracking experiments of a bird using satellite telemetry was reported by Jouventin and Weimerskirch (1990), who showed that wandering albatrosses (Diomedea exulans) remain active at night, fly at speeds of up to 80 km/hr, and range over distances of up to 900 km per day. Albatrosses covered from 3,600 to 15,000 km in a single foraging trip during the time their mates had taken over the duties of incubation. Satellite tracking is best used in situations where conventional tracking techniques are not useful, such as animals that range widely or are in habitats where they cannot be followed. Compared with conventional radio-tracking, satellite tracking is less accurate and more expensive. Radio contact with migrating whooping cranes (Grus americana) was maintained by means of leg-band radio transmitters, antennas attached to aircraft struts, and radio receivers carried in the aircraft (Kuyt, 1992). Radio signals, which could be picked up from distances up to 155 km, allowed researchers to follow the cranes. Visual contact was maintained for up to 50 percent of the migration, enabling air crews to obtain data on flight behavior. In studies of marine species, specific problems arise because of diving and because of the effect of high electrolyte concentrations on the radio signals. A floating transmitter tethered to a swivel strapped to the tail stock was devised and successfully used in studies of manatees (Rathbun et al.,1987). Baits containing acoustic transmitters have been consumed by deepsea fishes. In conjunction with an automatic tracking system and cameras on the sea floor, this technique has allowed the tracking of the speed and direction of travel in deepsea scavenging fishes (Priede et al., 1991). A summary of standard radio-tracking techniques was presented by Mech (1983). Specific data for amphibians were reviewed in Heyer et al. (1994); data for mammals were reviewed in Wilson et al. (1996). Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 Techniques for Ecological and Behavioral Studies 397 FIGURE 14.10 Trumpeter swans (Cygnus buccinator) following an ultralight aircraft, a method designed to teach birds the ancient migratory route of their ancestors. ■ MAPPING TECHNIQUES Geographic Information Systems (GIS) technology is the computerized recording of data for a region, using geographic coordinates as the primary indexing system. The kinds of data that can be stored include presence or absence of a species, abundance of that species where it is present, ecosystem type, soil type, geology and physiography, land protection status, and many other variables. For example, most home range studies have focused only on the horizontal component of the landscape (planimetric area), where the slope of the terrain is assumed to be zero. Topography adds an important element to landscape because the slope of the terrain often fluctuates throughout the home range, and because changes in topography can increase the surface area. A GIS that incorporates topography can account for topographic changes and yield more accurate estimates of home range size (Stone et al., 1997). GIS systems are well adapted to using data from remote sensing sources. Detailed data on the actual vegetation of a geographical area are difficult to obtain from traditional vegetation maps, which often show the potential climax vegetation thought to characterize a region rather than the vegetation actually present. With improved satellite imagery and analysis, detailed data on the vegetation that actually exists can be determined on a grid scale and entered into the indexing system. Ideally, a GIS system permits data on a particular feature to be stored for all the geographic units included in the indexing system. With modern GIS systems, it should be possible to develop much more comprehensive databases than previously available for researchers and conservationists. ■ CENSUSING TECHNIQUES The word “census” is defined as a count, which usually includes details as to sex and age. A true census is a count of all individuals present in a given area. Because such counts of wild animals are rarely possible, estimates usually are made based on some sampling procedure. Sampling estimates are derived from counts made on sample plots or a portion of a population. These estimates have variability, but still permit inferences about the population. An index is a count of some object that is related in some numerical way to the animal, such as tracks, feces, call counts, or nests. For example, Richard and Karen Barnes developed the first standardized method for gauging elephant populations by counting dung piles along previously identified routes and inserting the results into a mathematical formula that considers rates of defecation and dung decay (Tangley, 1997). Similar methods have been developed for jackrabbit indexing (Blackburn, 1968). For population estimates to be valid, all members of a population must have an equal probability of being counted, or the relative probabilities of counting different categories of individuals (e.g., sex and age classes) must be known. Ani- mals must not group by sex or age; they must mix randomly; and they must not develop “trap-shyness” or “trap-happiness” if grid live-trapping is being employed (see Chapter 11). In addition, during the period when data are collected, either mortality and recruitment must be negligible, or the estimates must be corrected for these effects. Data may be gathered by visual observation or by evi- dences of an animal’s presence (tracks, calls, etc.). For instance, haypiles of pikas (Ochotona) may be found in late summer and fall and can be used as an index. The average distance between the haypiles of adjacent pikas is approximately 30 m (Smith, 1982). Another method of gathering data is by the use of a transect. Transects are predeter- mined routes that are covered in an effort to estimate a population. All animals that are sighted or heard are recorded. Transect data from different seasons and years provide relative estimates of population size. Many territorial species can be observed easily within their territories and counted for a specific area. The result usually is expressed as animals per hectare. However, nonterritorial individuals in these species often are hard to count. Animals that congregate in groups or flocks (e.g., coveys of quail, flocks of turkeys and other birds, herds of antelope and bison) are rel- atively easy to count either on the ground or by means of aerial photographs. In those species of frogs and birds that call or sing, the vocal members of the population can be counted. The National Audubon Society’s annual Christmas Bird Count provides an index of species’ abundance nationwide. The North American Breeding Bird Survey has provided valuable data on the sizes of breeding bird populations since 1965, especially those of neotropical migrants. Such databases are revealing steady population declines of breeding birds for many species in North America (see Chapters 15 and 16). Statistical estimates of population size based on sample plots, indices, rates of capture, changes in sex or age ratios, recaptures, or home range data can be calculated by many different methods (Mosby, 1963). The Lincoln Index (also known as the Petersen–Jackson Method because it was first used on wild populations of plaice by Petersen [1896]), for example, is based on the recapture of marked individuals where the population (N) is related to the number marked Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 398 Chapter Fourteen (a) (b) (c) V P V P If caught in December If caught in January (Assumed) Circuli Annuli 1 2 1 2 3 First year Second year FIGURE 14.11 and released (M) in the same way as the total caught at a sub- sequent time (n) is related to the number of marked individuals captured (m). Censusing methods, along with capture and marking techniques, have been discussed for game birds and mammals by Mosby (1963), for terrestrial vertebrates by Davis (1982), for amphibians by Heyer et al. (1994), and for mammals by Wilson et al. (1996). ■ AGING TECHNIQUES Many fishes, amphibians, and reptiles grow throughout their lives. This indeterminate growth is most rapid in younger individuals, and it may speed up when food and environmental conditions are favorable and slow down when conditions are more stressful, such as during periods of cold, drought, and food shortage. Birds and mammals generally experience a steady increase in size until they reach maturity, after which growth slows and essentially ceases for the remainder of their lives. This is known as determinate growth. Various methods of determining the age of vertebrates have been developed. Animals that are captured shortly after hatching or birth and that are marked and recaptured at periodic intervals provide the most accurate means of determining age under natural conditions. In some cases, direct observation of an animal’s life stage, physical features, and size can give an approximation of its age. Life cycles of most amphibians, for example, involve two, and sometimes three, distinct stages (larval or tadpole, and adult). Few long-term age-determination studies have been reported. In one long- term reptilian study, three-toed box turtles (Terrapene carolina triunguis) studied for 25 years had estimated ages ranging from 27 to 59 years of age at the conclusion of the study (Schwartz and Schwartz, 1991). Most young birds have several distinct juvenile and subadult plumages as they mature (natal down, juvenal plumage, first winter plumage, nuptial plumage; see Chap- ter 12 for detailed discussion of molts and plumages). Some birds, such as bald eagles, may not attain their full adult plumage until they are 3, 4, or even 5 years old. The pelage of many young mammals also differs from the adult pelage and is known as the juvenal pelage. When molting occurs, this pelage usually is replaced by the postjuvenal pelage and then by the adult pelage. More precise age-determination techniques vary among the vertebrates and involve features of the integumentary, skeletal, and even the nervous system. Some techniques are useful in field investigations with live animals, whereas others can only be used on dead specimens. For example, tem- perate zone fishes can be aged by examining the annuli on scales (Fig. 14.11a), bones, and ear-stones (otoliths) (Fig. 14.11b), and in cross sections of fin rays, fin spines, and vertebral centra. Many fish deposit otolith growth increments with a 24-hour periodicity (Pannella, 1971; Prince et al., 1991; Kingsmill, 1993). In some species, such as Atlantic salmon (Salmo salar), the scales may contain spawning marks. Exam- ination of such scales can provide information about when the fish first went to sea, its age when it first spawned, how many times it has spawned, and its age at capture. Because growth accelerates in the sea, annuli are more widely spaced. Annuli also are evident on the scutes of some turtles. Most juvenile turtles add single growth rings each year, whereas rings are added less frequently as adults (Galbraith and Brooks, 1989) (Fig. 14.11c). Moll and Legler (1971) reported that (a) A typical ctenoid scale, showing groups of concentric rings that can be classified into annuli and interpreted as seasonal growth marks. Source: Calliet, Love, and Ebeling, Fishes: A Field and Lab Manual, 1986, Wadsworth Publishing. (b) A fish otolith showing annuli. A year class and/or birth date can be assigned, using the time of year the fish was collected. (c) Growth lines (annuli) on the vertebral (V) and the pleural (P) shields of the terrapin (Malaclemmys) (left) and the box turtle (Terrapene) (right). In Malaclemys, embryonic shield areas are near the center of the shields; in Terrapene, they are eccentrically located, and growth proceeds primarily anteriorly and laterally. Source: (a) Calliet, Love, and Ebeling, Fishes: A Field and Lab Manual, 1986, Wadsworth Publishing. (c) Zangerl, “The Turtle Shell” in C. Gans, Biology of the Reptiles, 1969. Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 Techniques for Ecological and Behavioral Studies 399 multiple growth lines were added each year in a population of neotropical sliders (Pseudemys scripta) in Panama. Annual bone rings in the phalanges and femurs of lizards have been used to age such species as tuataras (Sphenodon) (Castenet et al., 1988). Klinger and Musick (1992) injected tetracycline into juvenile loggerhead turtles (Caretta caretta) in the Chesapeake Bay area and found annular deposition in bone layers. The condition of teeth is useful for establishing the age of mammals. Both the deciduous and permanent dentitions usually erupt in a definite sequence and at definite times in different species. Patterns of wear, particularly of the permanent dentition, provide a fairly accurate means of determining age, particularly in large herbivores (Fig. 14.12). In addition, roots of teeth in some mammals form annual (a) (b) (c) (d) (e) (g) (i) (f) (h) Progressive wear on the molars is used to determine the age of white-tailed deer (Odocoileus virginianus): (a) 1 year, 7 months; (b) 2.5 years; (c) 3.5 years; (d) 4.5 years; (e) 5.5 years; (f) 6.5 years; (g) 7.5 years; (h) 8.5–9.5 years; (i) 10.5 or older. Sources: Halls (ed.) in White-tailed Deer Ecology and Management, 1984, Stackpole Books, and Cockrum, Mammalogy, 1962, Ronald Press. FIGURE 14.12 [...].. .Linzey: Vertebrate Biology 400 14 Techniques for Ecological and Behavioral Studies © The McGraw−Hill Companies, 2003 Text Chapter Fourteen growth ridges on their surfaces The roots of teeth also may be sectioned to reveal the presence of growth rings or annuli Many... which it is present, and the development FIGURE 14. 13 Annual rings in the horn of a 10-year-old desert bighorn sheep (Ovis canadensis) of prominent crests and ridges on the skull, particularly in male mammals In addition, a number of species-specific aging techniques have been employed Among these are leg coloration in coots (Fulica), the size of spurs on ring-necked pheasants (Phasianus colchicus), and... indeterminate growth Give several examples 9 List several techniques used to determine the age of vertebrates 10 Which methods of age determination would be most appropriate for studying a population of marine toads (Bufo marinus) whose life expectancy may be as much as 8 years? Linzey: Vertebrate Biology 14 Techniques for Ecological and Behavioral Studies © The McGraw−Hill Companies, 2003 Text Techniques... populations Ecological Monographs 14: 67–106 Kunz, T H (ed.) 1988 Ecological and Behavioral Methods for the Study of Bats Washington, D.C.: Smithsonian Institution Press Lebreton, J.-D., and Ph M North 1993 Marked Individuals in the Study of Bird Populations Basel: Birkhauser Verlag Marion, W R., and J D Shamis 1977 An annotated bibliography of bird marking techniques Bird-Banding 48:42–61 McClure, H E... factors must be taken into consideration when designing a research program for a wide-ranging species such as a cougar? How would this differ from a prairie dog research study? 2 Discuss several techniques for capturing small mammals alive and uninjured 3 List several techniques for marking reptiles and mammals for short-term studies 4 List several techniques used to tag birds and mammals so that individuals... recognized at a distance 5 List several advantages and several disadvantages of attaching external radio transmitters to vertebrates 6 What are some advantages and some disadvantages of satellite tracking as compared with the use of radio transmitters? 7 List several ways of censusing vertebrate populations Which methods would provide the greatest amount of data for the spotted salamander (Ambystoma maculatum),... Reading Adler, B., Jr 1996 Outwitting Squirrels Chicago: Chicago Review Press Adler, B., Jr 1997 Outwitting Critters New York: Lyons and Burford Anderson, R M 1965 Methods of Collecting and Preserving Vertebrate Animals Fourth edition Bulletin No 69 Biological Series No 18 Ottawa: National Museum of Canada Berwick, S H., and V B Saharia (eds.) 1995 The Development of International Principles and Practices... Anderson, and J L Laake 1980 Estimation of density from line transect sampling of biological populations Wildlife Monographs 72: 1–202 Davis, D E (ed.) 1982 CRC Handbook of Census Methods for Terrestrial Vertebrates Boca Raton, Florida: CRC Press Emlen, S T 1971 Population estimates of birds derived from transect count The Auk 88:323–342 Heyer, W R., M A Donnelly, R W McDiarmid, L C Hayek, and M S Foster... cementum can be used to reconstruct the reproductive histories of female black bears (Coy and Garshelis, 1992) Mammals with permanent horns, such as sheep and goats, often possess ridges on their horns (Fig 14. 13) These ridges are the result of periods of good (summer) and poor (winter) food conditions When forage is good, the horns grow rapidly; when forage is poor, the horns stop growing The stoppage is... H S (ed.) 1963 Wildlife Investigational Techniques Second edition Washington, D.C.: The Wildlife Society Ralph, C J., and J M Scott (eds.) 1981 Estimating Numbers of Terrestrial Birds Studies in Avian Biology No 6 Columbus, Ohio: Cooper Ornithological Society Robbins, C S 1970 Recommendations for an international standard for a mapping method in bird census work Audubon Field Notes 24:723–726 Svenson, . Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 CHAPTER 14 Techniques for Ecological and. use of radio transmitters, and satellite tracking. Linzey: Vertebrate Biology 14. Techniques for Ecological and Behavioral Studies Text © The McGraw−Hill Companies, 2003 392 Chapter Fourteen A. and (c) oscillating pattern. Sunrise (↑) and sunset (↓) are indicated on the time axis. Source: Data from Peterson in Ecology, 68(1)1987. FIGURE 14. 9 Linzey: Vertebrate Biology 14. Techniques