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Populations of the desert tortoise, Gopherus agassizii, have been severely impacted by upper respiratory tract disease (URTD), a potentially fatal condition caused by Mycoplasma agassizii. Because natural communities of microorganisms in animals may serve as barriers to infection by potential pathogens or may influence the course of a disease, we characterized the bacteria in the nasal passages of captive desert tortoises over an entire season. Tortoises housed in outdoor pens at the Adobe Mountain Wildlife Center in Phoenix, AZ, were divided into four groups: three healthy tortoises that were sampled monthly, three tortoises with signs of URTD that were sampled monthly, three healthy tortoises that were sampled bimonthly, and three healthy tortoises that were sampled once at the end of the season. At each sampling time, the health of each tortoise was assessed and the nares were probed with moistened sterile swabs. The bacteria on the swabs were suspended in sterile saline, serially diluted, and...

Extant amphibians comprise three lineages-- salamanders (Urodela or Caudata), frogs and toads (Anura), and caecilians (Gymnophiona, Apoda, or Caecilia)--which contain more than 6,000 species. Fewer than a dozen species of amphibians are commonly maintained in laboratory colonies, and the husbandry requirements for the vast majority of amphibians are poorly known. For these species, a review of basic characteristics of amphibian biology supplemented by inferences drawn from the morphological and physiological characteristics of the species in question provides a basis for decisions about housing and feeding. Amphibians are ectotherms, and their skin is permeable to water, ions, and respiratory gases. Most species are secretive and, in many cases, nocturnal. The essential characteristics of their environment include appropriate levels of humidity, temperature, and lighting as well as retreat sites. Terrestrial and arboreal species require moist substrates, water dishes, and high relative humidity. Because temperature requirements for most species are poorly known, it is advisable to use a temperature mosaic that will allow an animal to find an appropriate temperature within its cage. Photoperiod may affect physiology and behavior (especially reproduction and hibernation), and although the importance of ultraviolet light for calcium metabolism by amphibians is not yet known, ecological observations suggest that it might be important for some species of frogs. Some amphibians are territorial, and some use olfactory cues to mark their territory and to recognize other individuals of their species. All amphibians are carnivorous as adults, and the feeding response of many species is elicited by the movement of prey. Diets should include a mixture of prey species, and it may be advisable to load prey with vitamins and minerals.

Fossorial lizards differ in morphology from their surface-dwelling relatives. The Australian sphenomorphine skink genus Ctenotus consists of surface-dwelling species, and is closely related to the genus Lerista, which includes both surface-dwelling and fossorial species. Sand-swimming represents the derived condition and has evolved independently in several lineages of Lerista. The heads of lizards in the two genera differ in shape (blunt snout for Ctenotus versus wedge-shaped for Lerista) and in length relative to the body (approximately 20% of snout-vent length for Ctenotus versus 12% for sand-swimming Lerista). Do these specializations affect the sizes or types of prey that can be consumed by Lerista? We compared prey-handling by Ctenotus and Lerista to correlate morphological differences with differences in prey-handling ability, and to distinguish the effects of snout shape and head length. Feeding trials included three categories of insect prey that the lizards normally eat: soft-bodied larvae (Lepidoptera), hard-bodied larvae (Coleoptera), and roaches (Blatoidea). In comparisons based on the mass of a prey item relative to the mass of a lizard, Lerista had longer handling times for all prey categories and were limited to smaller prey than were Ctenotus. However, when comparisons were based on the length of prey relative to the length of a lizard's head, Lerista ate some elongate prey as fast or faster than did Ctenotus, and both genera successfully swallowed prey more than twice the length of their own head. Thus, the differences in prey-handling performance of Ctenotus and Lerista probably result from the fact that Lerista have a relatively shorter head than Ctenotus. All Lerista species, surface-dwelling and fossorial, have short heads compared to primitive sphenomorphine lizards. Fossorial species of Lerista have elongate trunks, and consequently their heads are shorter in proportion to trunk length than those of surface-dwelling Lerista. However, most fossorial species of Lerista are longer and heavier than any of their surface-dwelling congeners, and the heads of these fossorial species are large relative to the prey they encounter. As a consequence, the diets of large fossorial species of Lerista do not appear to be limited by their morphological specialization for sand-swimming.

The foraging and social behaviour of four species of Panamanian dart-poison frogs, Dendrobatidae, were recorded and that information was combined with an analysis of aerobic and anaerobic metabolism and with published information about food habits to test predictions about associations among behavioural, ecological and physiological characteristics of anurans. Several generalizations were supported by the data. The widely foraging species of frogs made more prey capture attempts in total and took more prey at each feeding station than did the sedentary species. The widely foraging species had higher capacities for aerobic metabolism and lower anaerobic capacities than did the sedentary species. Other generalizations were not supported. Dietary habits were only loosely related to foraging mode and neither aerobic capacity nor foraging mode was a good predictor of the frequency of vocalization or of agonistic behaviour. High aerobic capacity and widely foraging behaviour may be derived characters in the family Dendrobatidae, but the metabolic and behavioural requirements of territorial defence provide an alternate hypothesis for the association of some ecological and physiological characteristics of frogs.

Temperature and humidity are dominant environmental variables affecting performance of nocturnal, terrestrial amphibians. Toads are frequently active at body temperatures (T(b)) and hydration states (HS) that yield suboptimal performance. We investigated the combined effects of T(b) and HS on feeding, locomotion, and metabolism of Bufo americanus. More toads responded to the presence of prey when fully hydrated than when dehydrated, and times to orient to prey, maneuver around a barrier, and reach prey were less in hydrated than in dehydrated animals. Time to capture prey decreased with increasing T(b) in fully hydrated, but not dehydrated, toads, and hydrated animals caught prey more rapidly than did dehydrated animals. Distance traveled in 5 min and aerobic scope were affected by T(b). Generally, individuals that performed well in the feeding experiments at a particular T(b) and HS also performed well at a different T(b) and HS. The same was true for distance traveled and aerobic scope. However, within combinations of T(b) and HS, correlations between performance variables were minimal. Specialization of a particular variable resulting in high performance at a certain T(b) and HS does not appear to exact a cost in terms of performance at a different T(b) and HS.

Most of the 9300 extant species of non-avian reptiles are squamates (lizards and snakes); there are only 315 extant species of turtles, 23 crocodilians, and one rhynchocephalian. Although the diversity of reptiles is greatest in the tropics, many species occur in the temperate regions and a few have geographic ranges that extend north of the Arctic Circle. Antarctica is the only continent with no extant reptiles. Ectothermy, an ancestral character, is central to the biology of reptiles, and is responsible for their low metabolic rates and their high efficiency of secondary production. Temperature-dependent sex-determination is universal in crocodilians, widespread among turtles, and present in some lineages of squamates. Among lizards, the mode of predation – sit-and-wait, cruising forager, or widely foraging – has a strong phylogenetic component and correlates with many elements of their ecology, morphology, physiology, and behavior. Lizards typically eat daily and consume many small prey items, whereas snakes eat less frequently and consume larger prey items relative to their body size. Most species of reptiles are small, inconspicuous, and have little obvious economic value, and as a consequence we lack information about the viability of their populations. Climate change, habitat loss, and pollution (including the feminizing effects of estrogen analogs) affect many species, and nearly three million lizards, snakes, turtles, and crocodilians are consumed by trade in hides and pets annually. The life histories of most large species of turtles, lizards, snakes, and crocodilians depend on prolonged adult survival and reproduction, and it is unlikely that these species will long withstand the current rate of commercial exploitation.

Many plethodontid salamanders establish feeding territories. We studied interactions of two species in different genera to investigate the roles of species identity, residency, and relative body size in gaining or maintaining control of a cover object. Species identity had the largest effect, with Desmognathus ochrophaeus proving more successful than Plethodon cinereus as a resident and as an intruder. Residency also influenced the outcome of trials: residents were more likely to maintain control of their cover objects than to be displaced. The relative body size of the salamanders in a trial had a small, marginally nonsignificant effect on the outcome. Species identity may be important in determining spatial relations of salamanders in the field. Foraging by plethodontid salamanders is re- stricted by dryness of the habitat. When the forest is wet, plethodontids forage widely and even climb plants in search of prey (Jaeger, 1978). When the forest becomes drier, activity

1. 1. Oxygen affinity of whole blood of 51 species of lizards from 12 families was measured at the eccritic temperature of each species. 2. 2. Blood oxygen affinity was lower than that of birds or mammals and increased with increasing body size. 3. 3. Iguanid lizards were used as a basis for comparisons of other families. Blood oxygen affinity of lizards in the families Agamidae, Cordylidae, Lacertidae and Varanidae did not differ from that of iguanids of comparable body size. 4. 4. Teiid and anguid lizards had lower oxygen affinities than iguanids. possibly reflecting their more active lives. 5. 5. Scincid and chamaeleonid lizards had higher blood oxygen affinities than iguanids, apparently as a result of their lower eccritic temperatures. 6. 6. Geckonid and xantusiid lizards had higher blood oxygen affinities than iguanids at their normally low eccritic temperatures and at higher temperatures comparable to eccritic temperatures of iguanid lizards.

Leptodactylid frogs (Eleutherodactylus coqui Thomas) reduce rates of evaporative water loss threefold by adjusting their postures and activities in response to changing conditions of availability of water during their nocturnal activity periods. Frogs that do not make these adjustments experience a potentially lethal loss of body water on a rainless night. Dehydration of a frog's body tissues increases its resting metabolic rate and lowers its maximum rate of aerobic metabolism. Water is reabsorbed from urine in the bladder to maintain tissue water content on dry nights. Use of water—conserving postures precludes vocalization by male frogs and response to calling males by females. Frogs in water—conserving postures feed less readily than active frogs. Frogs in the forest canopy experience higher rates of evaporative water loss than those in the understory, but there are more anthropods in the canopy, and leaf surfaces are twice as likely to be wet by rain. Despite these potential benefits of activity in the forest canopy, most frogs remain in understory vegetation. In that microhabitat their behavioral and physiological adjustments permit them to occupy their normal perches despite wide fluctuations in hydric conditions.

We measured the oxygen consumption (aerobic energy cost) and lactic acid production (anaerobic energy cost) of scincid lizards, Chalcides ocellatus, eating domestic crickets. Aerobic metabolism accounted for 90% or more of the total energy cost of subduing and swallowing prey. The time required to subdue and swallow a cricket was linearly correlated with oxygen consumption. Oxygen consumption increased as a power function of cricket mass, but the maximum size of crickets swallowed by the lizards was set by morphological rather than by energetic constraints. The energy cost of subduing and swallowing was 0.2—0.4% of the utilizable energy of the cricket eaten. Net energy gain per unit time spent subduing and swallowing prey (e/t) declined monotonically with increasing cricket mass. Because the energy cost of eating is trivial, the shape of the e/t curve is determined by the function relating prey mass to the time required for subduing and swallowing; the energy value of prey was proportional to prey mass, whereas the time required for subduing and swallowing increased faster than prey mass. The energy value of anthropods is so high, relative to the costs for a lizard of pursuring, subduing, and swallowing, that these costs can be ignored for most ecological purposes.

Newly-metamorphosed individuals of some species of frogs and toads differ from adults in behavior, ecology, and physiology. These differences may be related to broader patterns of the life histories of different species of frogs. In particular, the length of larval life and the size of a frog at metamorphosis appear to be significant factors in post-metamorphic ontogenetic change. These changes in performance are associated with rapid post-metamorphic increases in oxygen transport capacity. Bufo americanus (American toads) and Rana sylvatica (wood frogs) spend only 2-3 months as tadpoles and metamorphose at body masses of 0.25 g or less. Individuals of these species improve endurance and aerobic capacity rapidly during the predispersal period immediately following metamorphosis. Increases in hematocrit, hemoglobin concentration, and heart mass relative to body mass are associated with this improvement in organismal performance. Rana clamitans (green frogs) spend from 3 to 10 months as larvae and weigh 3 g at metamorphosis. Green frogs did not show immediate post-metamorphic increases in performance. Rana palustris (pickerel frogs) are intermediate to wood frogs and green frogs in length of larval life and in size at metamorphosis, and they are intermediate also in their post-metamorphic physiological changes.American toads and wood frogs appear to delay dispersal from their natal ponds while they undergo rapid post-metamorphic growth and development, whereas green frogs disperse as soon as they leave the water, even before they have fully absorbed their tails. The very small body sizes of newly metamorphosed toads and wood frogs appear to limit the scope of their behaviors. The brief larval periods of these species permit them to exploit transient aquatic habitats, but impose costs in the form of a period of post-metamorphic life in which their activities are restricted in time and space compared to those of adults.

At birth the blood of garter snakes (Thamnophis sirtalis) has high oxygen affinity (P50 at 25 degrees C and pH 7.2 = 21 mm Hg), low hematocrit (14%), and a high proportion of inactive hemoglobin (44%). Growth of the snakes is accompanied by a steady decrease in oxygen affinity (P50 = 44 mm Hg in adults), increased hematocrit (to 44%), and decreased inactive hemoglobin (to 3%). These adult values are reached in the second or third year of a snake's life. There is a continuous change in the electrophoretically separable hemoglobin fractions during this period, but there is no ontogenetic change in the oxygen affinity of phosphate-stripped hemoglobin in solution. Organic triphosphates do not fully explain the ontogenetic change in blood oxygen affinity. Similar ontogenetic changes in blood oxygen affinity were found in two other species of snakes. The unusual morphology of snake lungs and consequent changes in pulmonary pO2 and pCO2 during ontogeny may be the basis for the unusual relationship between body size and blood oxygen affinity in snakes.

In the Puerto Rican frog Eleutherodactylus coqui, parental care is performed exclusively by males, and consists of attending the eggs and hatchlings at a terrestrial oviposition site. The two major behavioural components of parental care are egg brooding and nest defence against conspecific egg cannibals. Defence behaviour includes aggressive calling, biting, sustained biting, wrestling, and blocking directed against nest intruders. Parental care lasts from oviposition to hatching (17–26 days) and often for several days after hatching. During pre-hatching development, males are present in their nests 97.4% of the time during the day and 75.8% of the time at night. A large portion of this time is spent brooding eggs. In a field experiment, males were removed from their nests and the fate of clutches was monitored. Compared to control clutches (males not removed), experimental clutches had significantly lower hatching success and suffered significantly greater mortality from desiccation and cannibalism. Hence, parental care yields significant benefits to male fitness via increased offspring survival.

We used multiple regression analysis to evaluate the relationship between metabolic rate and three independent variables-mass, temperature, and standard or resting state-for squamate reptiles. For comparisons among adults of different species, mass raised to the .80 power explains 88% of the variation in metabolic rate. (The .80 mass exponent is significantly greater than the .75 predicted by theoretical considerations.) A further 8% of the variation in metabolic rate is explained by body temperature and whether the lizard is in a standard or resting metabolic state. Residuals were used to determine whether metabolic rates varied as a function of phylogenetic relationship or ecological grouping. Familial associations explained 16% of the variation in metabolic rate for varanids, lacertids, iguanids, colubrids, scincids, xantusiids, gekkonids, and boids. More variation (45%) was explained when lizards were partitioned into four ecological categories: day-active predators, hervibores, reclusive predators, a...

1. 1. We measured standard, resting and exercise metabolism of 28 Chaicides ocellatus (Scincidae). Individual lizards consistently showed statistically significant differences in mass-independent rates of standard and exercise metabolism during three replicates of the experiments at weekly intervals. 2. 2. Metabolic differences were also detected among groups of siblings. 3. 3. Mass-independent resting metabolic rates were closely correlated with standard rates, but there was no correlation of metabolic rates during forced activity with either standard or resting rates. 4. 4. These data suggest a heritable component of metabolism for lizards, but they do not support the “aerobic capacity model” of the origin of endothermy, which proposes that initial selection for high resting metabolic rates operated via selection for high rates of aerobic metabolism during exercise.

The popular view of the Age of Reptiles as a Mesozoic phenomenon that closed with the extinction of dinosaurs does not consider the remarkable evolutionary success of one group of living reptiles, the snakes. This suborder of the Squamata is first known from Cretaceous fossils of extinct groups and boa-like forms (Hoffstetter, 1962). Ancestors of modern snakes, the Caenophidia, appeared in the Paleocene and their radiation in the second half of the Cenozoic has been so rapid and extensive that the Neogene could appropriately be known as "The Age of Snakes" (Stanley, 1979). What is it about snakes that has made them so successful? The elongate, legless serpentine body form is a distinctive characteristic of snakes and it influences all areas of their biology. Snakes differ markedly from their closest relatives, the lizards, in body size. Most lizards are small animals weighing less than 20 g as adults and feed on insects. Nearly 80% of living lizard species fit that description and morphological adaptations that appear to be related to insectivorism as a dietary specialty have characterized lizards from their initial appearance in the fossil record (Carroll, 1977: Pough, 1980). In contrast, nearly 75% of snake species have adult body masses greater than 20 g. Because most small mammals also have body masses of 20 g or more, the disparity of body sizes of snakes and lizards places these two suborders of squamate reptiles in quite different relationships with mammals. Lizards appear to avoid competition

1. 1. Male spring peepers ( Hyla crucifer ) were captured as they vocalized in a breeding chorus and immediately frozen in liquid nitrogen. 2. 2. These frogs had whole-body lactic acid concentrations nearly twice those of control frogs resting in the laboratory at the same temperature and time of day. 3. 3. We suggest that the energetic cost of vocalization for spring peepers exceeds their anaerobic threshold, and activity of the muscles involved in calling is supported partly by anaerobic metabolism.

Metabolic correlates of prey preference were evaluated in four species of tropical frogs. Predation on ants and termites is correlated with high aerobic capacity, low anaerobic capacity, and high resting metabolism. In contrast, dependence on larger, more mobile prey such as orthopterans and coleopterans is associated with low aerobic capacity, high anaerobic capacity, and low resting metabolism. These correlations presumably stem from the metabolic demands of different foraging behaviors. Characteristics of both the predator and the prey interact to create these demands, thereby producing a spectrum of foraging modes. Locomotion, agonistic behavior, and reproductive characteristics also can be intimately associated with metabolic capacities. The exercise physiology of predators reflects the complexity of this situation.

The response to simultaneous temperature and dehydration stress was examined in three species of Puerto Rican frogs.Eleutherodactylus antillensis is found primarily in hot, arid grasslands at low altitudes.Eleutherodactylus portoricensis is restricted to cool, forested montane habitats above 300 m.Eleutherodactylus coqui occurs in both the lowlands and the highlands. The physiological tolerance of the frogs to temperature was measured at 20, 25, and 30°C at various levels of dehydration using an index derived from jumping performance. Although jump distance of fully hydratedE. antillensis was unaffected by temperature, this species tolerated significantly more dehydration at high temperatures than low.Eleutherodactylus portoricensis died at 30°C, but in this species both distance jumped and dehydration tolerance were unaffected by lower temperatures. Distance jumped byE. coqui increased with increasing temperature, but tolerance of dehydration remained unchanged.Eleutherodactylus coqui was less tolerant of high temperatures thanE. antillensis but more tolerant thanE. portoricensis.

We measured handling time and oxygen consumption for the scincid lizard Chalcides ocellatus feeding on crickets at temperatures of 25, 30, and 35 C in the laboratory. The time required for manipulating prey in the mouth and swallowing did not change significantly with temperature. The total net aerobic cost of handling, measured as the oxygen consumption in excess of resting levels during both handling and the 30 min immediately following handling, had a $Q_{10}$ of 1.9 from 25 to 35 C. For this system we conclude the following: (1) Time and energy costs of handling are differentially affected by temperature; thus, the two measures cannot be used interchangeably as measures of relative cost for feeding bouts that occur at different temperatures. (2) The $Q_{10}$ for the total net aerobic cost of handling in C. ocellatus (1.9) is consistent with results of previous work on the energetic cost of locomotion in the agamid lizard Uromastix aegyptius ($Q_{10} = 1.6$), and on isometric force generation in isolat...

Blood oxygen affinity of 15 species of colubrine snakes is related to body size by the equation $P_{50}(mm Hg) = 21.54 + 7.39 log wt (g)$. Blood oxygen affinity of snakes in six other families did not differ from values predicted for colubrines of the same body size. An ontogenetic decrease in blood oxygen affinity was found in three of four species for which adequate samples were available. This ontogenetic change was seen only in whole blood; there was no ontogenetic change in oxygen affinity of hemoglobin in solution. The decrease in blood oxygen affinity with increasing body size (ontogenetic growth or adult body size) in snakes contrasts with the increase in oxygen affinity with increasing body size in mammals, birds, and lizards. The difference in blood oxygen affinity probably reflects the differences in pulmonary gas concentrations produced by specialized lung morphology and breathing movements of snakes.

1. 1. The apparent efficiency of assimilation of preformed water from both plant and animal diets by the lizard Dipsosaurus dorsalis increased about 10% between 34 and 40 C. 2. 2. This increase parallels the increase in apparent digestibility coefficient of food and probably results from an osmotic balance between chyme and the intracellular fluid of the gut. 3. 3. Desert iguanas are largely subterranean in summer, spending almost 90% of the day in burrows. Under the conditions they encounter there, the increased assimilation of preformed water with increasing body temperature equals the increase in evaporative water loss.

Oxygen capacity of reptile blood in vitro is temperature sensitive and is reversibly reduced as much as 40% at the extremes of the temperature range that animals normally encounter. In several species of lizards and snakes, blood oxygen capacity is maximum within the species' activity-temperature range. The correlation coefficient between eccritic temperature and the temperature giving maximum blood oxygen capacity for all species tested was .79 (P < .01). (When the genera Sceloporus and Uta, which show a different pattern, are omitted from the analysis, the correlation coefficient for the remaining species rises to .92.) This adaptation of the blood is one of the mechanisms that produces maximum oxygen consumption near a species' eccritic temperature. In lizards of the genera Sceloporus and Uta and in turtles the maximum blood oxygen capacity occurs at the bottom of the activity-temperature range and may reflect adaptation of these animals to activity at low temperatures.

There is an ontogenetic increase in the time that garter snakes (Thamnophis s. sirtalis) can maintain maximum activity at 25°C. Newborn snakes are exhausted by 3–5 min of activity while adults can be active for 20–25 min. The increased endurance of adult snakes results from ontogenetic increases in both aerobic and anaerobic energy generation. At rest juvenile and adult snakes have the same whole-body lactic acid concentrations, but at exhaustion adult lactic acid concentrations are 1.5 times those of juveniles. This increase in anaerobic energy production accounts for part of the endurance of adult snakes, but increased aerobic metabolism appears to be more important. Among the mechanisms increasing aerobic metabolism are more effective pulmonary ventilation and a 3-fold ontogenetic increase in blood oxygen capacity. The rapid exhaustion of small garter snakes probably limits the microhabitats they can occupy and the sorts of hunting methods they can employ. Small garter snakes feed only on small prey that are easily subdued. There is an ontogenetic increase in the relative size of prey eaten by garter snakes that parallels the ontogenetic increase in endurance. Adult feeding habits are adopted at the same body size at which adult blood oxygen capacity and endurance are attained.

1. 1.|We measured temperature resistance and lactic acid production of Notophthalmus viridescens and Plethodon cinerus acclimated to 10, 20 or 30°C. 2. 2.|Fatigue is responsible for the Loss of Righting Response (LRR) observed when Plethodon are heated and contributes to the LRR of Notophthalmus efts. 3. 3.|LRR is purely a manifestation of incapacitation by high temperature in Notophthalmus adults. 4. 4.|The Critical Thermal Maximum (CTM) is solely a product of temperature incapacitation in all three forms. 5. 5.|The standard test for temperature resistance should be expanded to include tests of fatigue.

The terrestrial eggs of the coqui of Puerto Rico are brooded almost continuously by the male parent from the time of oviposition until the fully metamorphosed hatchlings emerge from the eggs 15-20 d later. The gelatinous layer surrounding each egg offers no resistance to the exchange of water by the egg, and rates of exchange are determined by microclimatic conditions, structural characteristics of the nest, and the behavior of the male frog. During development in natural nests, the eggs experience a three- to fourfold increase in mass. Laboratory experiments coupled with field observations indicate that this increase is the result of the transfer of liquid water from the incubating male to his eggs. The transfer is driven by a difference in water potential between the eggs and the body fluids of the male frog that is nearly constant throughout incubation, despite an increase in egg mass. Eggs must take up water during incubation. Eggs that do not experience an increase in mass during development either die or produce small hatchlings. A water uptake that doubles the initial mass of the egg is necessary to produce a full-size hatchling with normal tissue water content.

Organismal performance lies at the base of ecological and evolutionary processes, and the consequences of individual variation in performance have become a focus of physiological ecology. The study of the relations of performance to Darwinian fitness integrates the traditionally reductionist approach of physiological ecology with the perspectives of genetics and evolution. Four levels of biological organization have been included in this effort: the description of genetic variation, the analysis of biochemical and physiological consequences of that variation, the description of variation in the capacity of individuals to perform various activities, and the analysis of the effect of that variation in performance capacity on individual variation in Darwinian fitness. Mechanisms within each of those levels have been elaborated, and cause-and-effect links have been established among the levels. Two approaches to defining causal links are prominent. The gene-to-performance school begins with the observation of...

Eleutherodactylus antillensis is a climbing frog that is widely distributed in grassy lowland habitats that often become dry between rainstorms. The closely related species E. coqui has an altitudinal range that extends from the same lowland sites occupied by E. antillensis to mountaintops that are almost continually wet. The frogs lose a substantial quantity of water by evaporation during activity on dry nights and can regain that water by absorption from the substrate of their daytime retreats. Lowland frogs of both species rehydrate more rapidly from aqueous solutions than highland E. coqui. When water uptake is expressed per cm² of surface area, E. antillensis rehydrates more rapidly than E. coqui. This relationship probably represents differences in hormonal responses to dehydration. These responses are complex because the rate of water uptake is not related to solution water potential by a simple physical relationship. The small body sizes of E. antillensis and lowland E. coqui probably facilitate r...

Examples of mimicry among vertebrates are numerically fewer than examples involving insects. The relatively small number of species of vertebrates, compared with the number of species of insects, probably explains some of the apparent scarcity of mimicry. Possibly more important is a mismatch between the primarily visual sensory world of humans and the predominantly chemosensory, auditory, and tactile worlds of most other vertebrates, which has probably concealed many manifestations of mimicry. Systematic investigation of the information that vertebrates convey through these sensory modalities will probably reveal many additional examples of mimicry. Concrete homotypies-those cases in which the model can be identified as a particular species of animal-are widespread among fishes and amphibians and have been suggested for birds and mammals. Both Batesian and Mullerian protective mimicry systems have been described. Because vertebrates grow during their lifetimes without conspicuous changes in morphology, s...

Cenozoic reptiles are characterized by physiological morphological and ecological systems with low energy requirements compared to those of mammals. Ectothermy and low resting rates of metabolism are the primary physiological adaptations of reptiles that produce low energy demand. Adjustments of the oxygen-transport system to different thermoregulatory characteristics among reptiles may be reflected in blood viscosity oxygen capacity oxygen affinity and the temperature sensitivity of oxygenation. Other adaptations reduce the energy cost of oxygen transport. Reptiles have low hematocrits and large, widely spaced capillaries that contribute to a low fluid resistance in the vascular system but also limit the oxygen transport capacity. The low oxygen affinity characteristic of the blood of most reptiles appears to facilitate diffusion of oxygen to the tissues, overcoming the intrinsic limitations imposed by the morphological specializations of the cardiovascular system. The low blood oxygen affinity permits virtually all of the oxygen carried by the blood to be delivered to the tissues during periods of stress. It may also help to maintain a relatively high arterial Po2 even when a right-to-left shunt occurs in the heart. Reptilian erythrocytes are capable of reducing methemoglobin rapidly. The high concentrations of methemoglobin and polymerized hemoglobin that occur in vivo may indicate that these compounds have a functional role. In their blood physiology as in other aspects of their biology reptiles are specialized animals that reflect selective forces quite different from those that have shaped the evolution of mammals.

Following metamorphosis, juvenile toads form dense, heliothermic aggregations on the margins of the ponds from which they emerge. After a period of growth and development, during which body mass increases ten-fold, the juveniles disperse from the pond and assume the solitary, nocturnal habits that characterize adult toads. The dispersal of the toads coincides with the culmination of ontogenetic changes in activity metabolism. Unlike adults, juvenile toads exhaust rapidly when exercised and exhibit a low aerobic component of total metabolic scope. Values of aerobic scope for sustained activity ranged from 0.5 ml O2/(g·h) for the smallest juveniles to 1.0 ml O2/(g·h) for adults. The capacity of juveniles for oxygen consumption increases rapidly with growth, reaching the level of mature animals immediately prior to dispersal. In contrast to aerobic metabolism, anaerobic scope was independent of body size. Whole body lactate content after a 1 min bout of vigorous activity was elevated above the resting level by 0.14 mg lactate/g for both juvenile and adult animals. The elevated body temperatures that are achieved by basking juvenile toads probably hasten their physiological development and increase their capacity for aerobic metabolism.

Studies of exercise physiology of anuran amphibians have led to the suggestion that there is a dichotomy between species that depend upon movement to escape from predators and species that utilize static defenses. This generalization has been based upon a limited taxonomic survey and it contrasts with morphological, ecological, and behavioral studies that have revealed diverse and complex interrelationships among these features of anuran biology. We tested the hypothesis of a dichotomy of physiological types among anurans by measuring aerobic and anaerobic metabolism during maximum exercise for 17 species representing seven families and a variety of ecological types and locomotor modes. All degrees of dependence upon aerobic and anaerobic power input were found among the 17 species and the variation did not follow phylogenetic divisions. No single, simple prediction of the predominant source of power utilized for activity by the anurans we studied is possible. Predator avoidance behavior was not significantly correlated with the metabolic pattern. Predatory mode (active versus passive searchers) and mode of locomotion (non-jumpers versus jumpers) were correlated with dependence upon aerobic energy production and with each other. Reproductive behavior is probably another associated factor. The diversity of modes of power input among anurans is great and is intimately linked with numerous features of a species' biology. Single-factor explanations of this physiological characteristic are not appropriate.

The way of life of amphibians and reptiles, in contrast to that of birds and mammals, is based on low energy flow. Many of the morphological and physiological characteristics of ectothermal tetrapods that are normally considered to be primitive are in fact adaptations that facilitate a life of low energy demand. Their modest energy requirements allow amphibians and reptiles to exploit various adaptive zones unavailable to birds and mammals. Small body size is the most important of these; 80% of all lizard species and 90% of salamanders have adult body masses less than those of small birds and mammals. An elongate body form, a widespread and successful morphotype among amphibians and reptiles, is energetically unfeasible for endotherms. Amphibians and reptiles also are better suited than birds and mammals to ecological situations characterized by periodic shortages of food, water, or oxygen. At the ecosystem level, the most important consequence of the low energy requirements of amphibians and reptiles is ...

Pough, F.H., Smith, E.M., Rhodes, D.H. and Collazo, A., 1987. The abundance of salamanders in forest stands with different histories ofdisturbance. For. Ecol. Manage., 20: 1-9. Because of the importance of salamanders in forest food chains, the effects of forest manage­ ment practices on populations ofthese animals warrant consideration. We compared the numbers and activity patterns of salamanders in areas of a deciduous forest in central New York State that had been cut selectively for firewood, or c1earcut, or planted with conifers. Numbers of salaman­ ders were lower in three recently disturbed habitats than in adjacent old-growth control stands. The frequency of above-ground activity by both species of salamanders was positively correlated with the density of understory vegetation and the depth ofle~ litter. Small-scale habitat disrup­ tion associated with harvesting firewood increased the numbers of the terrestrial eft stage of the red-spotted newt (Notophthalmusviridescens) but had no effect on numbers of red-backed sal­ amanders (Plethodon cinereus). A recently clearcut area had fewer red-backed salamanders than adjacent old-growth forest had, but the numbers of salamanders in a 60-year-old second-growth forest were indistinguishable from those in the adjacent old-growth forest. Populations of sala­ manders in a conifer plantation were low. Thus, salamanders seem to be resilient to limited dis­ turbance of forests, but major changes are likely to affect populations of salamanders and, consequently, of birds and mammals that depend on salamanders for food.

Viperid snakes have stouter bodies, larger heads, and longer jaws than snakes in other families; there are no major differences between the two subfamilies of vipers in these features. A suite of morphological characters that facilitates swallowing large prey finds its greatest expression among vipers, but certain elapid and colubrid snakes have converged upon the same body form. The number of jaw movements required to swallow prey is linearly related to the size of a prey item when shape is held constant. Very small and very large prey are not disproportionately difficult for a snake to ingest. Vipers swallow their prey with fewer jaw movements than do colubrids or boids and can swallow prey that is nearly three times larger in relation to their own size. Proteolytic venom assists in digestion of prey, and melanin deposits shield the venom glands from light that would degrade the venom stores. Ancillary effects of the morphological features of vipers, plus the ability to ingest a very large quantity of food in one meal, should produce quantitative and qualitative differences in the ecology and behavior of vipers and other snakes.

The teiid lizardAmeiva quadrilineata has a nasal salt gland that responds to NaCl loading by increasing excretion of Na+ (from 1.12 to 2.63 μM/100 gh), K+ (from 0.14 to 2.43 μM/100 gh), and Cl− (from 1.10 to 5.47 μM/100 gh). For salt-loaded lizards these values represent 47% of the total excretion of Na+, 35% for K+, and 87% for Cl−. The lizards forage on beaches and their diet includes large numbers of amphipods (Talorchestia) which are approximately twice as salty as the lizards' body fluids. All of the ingested Na+ and K+ can be excreted through the cloaca, but extra-renal excretion of Cl− is probably important to the lizards under natural conditions.

1. 1. Oxygen affinity of blood of five lizard species was measured at 25, 35 and 40°C and p CO 2 's of 38 and 76 mm Hg. 2. 2. At its activity temperature each species had a P 50 of 68–72 mm Hg. Oxygen affinity was also related to body size. 3. 3. There was a seasonal shift in oxygen affinity in Dipsosaurus dorsalis . 4. 4. There was no difference in oxygen affinity of blood of Sceloporus occidentalis from sea level and from 6000 ft. 5. 5. There was no correlation between sensitivity to CO 2 and fossorial habits. 6. 6. An anguid ( Gerrhonotus multicarinatus ) showed less sensitivity to changes in temperature and p CO 2 than iguanids.

1. 1. The elephant trunk snake (Acrochordus javanicus)is highly adapted morphologically for aquatic life. 2. 2. Unrestrained snakes spent the day resting quietly on the bottom of their tank; breathing was infrequent and accompanied by pronounced tachycardia. 3. 3. At night snakes swam continuously; breathing was more frequent and respiratory tachycardia was reduced. 4. 4. Snakes heated faster than they cooled when moved between water temperatures of 15 and 35°C because swimming at the higher temperature facilitated convective heat transfer. 5. 5. The heart rate at a given body temperature was the same whether snakes were heating or cooling in air or in water. 6. 6. Acrochordus' major adaptations for aquatic life are behavioral and morphological.

The theory of automimicry is explored mathematically on the assumption that predators can learn to avoid noxious prey by sight for some finite period after a single noxious experience. Automimetic advantage is an inevitable consequence of the evolution of an unpalatability dimorphism. An established automimetic situation is analogous to an established perfect Batesian mimicry situation, although the evolutionary bases of the two phenomena are different. In both situations, the mimetic advantage depends upon the proportion of unpalatable prey, the memory span of the predators, and the abundance of the prey relative to the predators. Automimetic advantage is maximal when the prey are neither too common nor too rare. Remarkably low proportions of unpalatable prey can confer very substantial immunity to the population. A surprising prediction of the model is that the evolution of unpalatability will not occur in rare prey species unless they first become Batesian mimics. This in turn could lead to the evolution of mimicry complexes containing many species forming a whole spectrum of unpalatability.

1. 1. Burrowing lizards (Uma and Callisaurus) were compared with the non-burrowing Disposaurus. All species showed alternating periods of apnea and eupnea. The length of apneic periods increased at low body temperatures. 2. 2. Bradycardia and tachycardia were associated with apnea and upnea, respectively. 3. 3. There was a temperature-independent increase in heart and breathing rates beginning 1 or 2 hr before “dawn”. 4. 4. On to five per cent CO2 in air decreased rate and increased amplitude of breathing movements of Uma and Dipsosaurus. Uma were more sensitive to elevated CO2 levels than Dipsosaurus. 5. 5. There were no physiological differences between Uma and Dipsosaurus that could be interpreted as adaptations for Uma's burrowing.

In the families Agamidae, Gerrhosauridae, Iguanidae, and Scincidae, species that weigh more than 300 g are almost all herbivores, whereas those weighing less than 50—100 g are carnivores. Juveniles of large herbivorous species tend to be carnivorous until they reach body weights of 50—300 g. Diet is compared to metabolic expenditure in these lizards. Although smaller animals have higher weight—specific metabolic rates, the greater total metabolicrate of larger animals requires a greater caloric intake. Juvenile animals and species of small body size are primarily insectivorous. It is postulated that larger animals of these families are unable to get caloric demands on a diet of insects, have no practical alternative animal prey, and rely instead on vegetation. The families Anguidae, Chamaeleontidae, Helodermatidae, Teiidae, and Varanidae do not include herbivorous species, although each family has species that weigh more than 300 g. Morphological, ecological, and physiological specializations in these families account for the absence of herbivorous species. For an unspecialized lizard, evolution of large body size both requires and permits an herbivorous diet.

1. 1.In the field, adult fringe-toed lizards (Acanthodactylus erythrusus) had a mean body temperature of 38.8 ± 0.2 (S.E.) °C while subadults maintained a significantly lowr temperature ( x = 35.4 ± 0.5°C ). 2. 2.Laboratory measurements of oxygen consumption, ventilation frequency, and heart rate indicate that temperatures above 38°C are stressful to subadults. 3. 3.Activity periods of subadults are curtailed by high temperatures for 3 months in summer while the activity of the more thermophilic adults is curtailed only during July and August. 4. 4.Some lizards maintained a high metabolic rate by achieving a low Q10 ( x = 1.3 ) between 13 and 25°C. 5. 5.Because these lizards initiate activity at black body temperatures of 13°C in their natural habitat, the ability to sustain high rates of aerobic metabolism at low temperatures is probably valuable.

The forest frog Eleutherodactylus coqui defends specific sites for retreats and nests in the Luquillo Forest, Puerto Rico. The hypothesis that shortages of nest and retreat sites limit population size was tested by placing 100 bamboo frog houses in plots measuring 100 square meters in areas of high frog density. These new sites were readily adopted by adult frogs. After one year, experimental plots had significantly more nests and frogs of all sizes than did control plots.

Eastern red-spotted newts (Notophthalmus viridescens, Salamandridae) are rarely attacked by leeches. This protection is not shared by related salamandrids or by Ambystoma (Ambystomatidae). Tetrodotoxin is not the repelent. The immunity of Notophthalmus to leech parasitism is probably most significant in its aquatic stages, although the terrestrial efts are also protected.

o 1. We determined the temperatures selected in a complex thermal gradient by salamanders acclimated to 5, 15 and 25°C. 2. There was an inverse relationship between acclimation temperature and selected temperature. 3. The temperatures selected by salamanders acclimated to 15°C increased from June through August and fell slightly in October. 4. Acclimation of selected temperature was faster and of greater magnitude than acclimation of temperature resistance.