Post-Strike Behavior of Timber Rattlesnakes (Crotalus horridus) During Natural Predation Events

The complexity of natural environments is an important component of animal behavior, and laboratory environments often cannot reproduce that complexity. Strike‐induced chemosensory searching (SICS) is a robust phenomenon among venomous snakes that has been studied extensively in the laboratory. To date, observations of this behavior in the field have been limited largely to anecdotes; the extent to which post‐strike behaviors in the laboratory accurately reflect what occurs in nature has not been examined. In this study, I use time‐lapse video equipment in the field to record the predatory behavior of timber rattlesnakes (Crotalus horridus). This represents the first quantitative analysis of post‐strike predatory behaviors associated with natural feeding events. As in the laboratory, stereotyped post‐strike behaviors were only observed after successful strikes, and not after missed strikes. Snakes in the field were observed to proceed through the same basic behavioral stages that have been documented in the laboratory: striking prey, releasing prey immediately after strike, post‐strike immobility, location of the chemosensory trail, trail following, and prey swallowing. However, the duration of post‐strike immobility, trail location, and prey swallowing was substantially longer in field than in laboratory studies. Additionally, post‐strike immobility was significantly longer when snakes struck large prey (prey over 100 g) than when they struck small prey. Overall, these results indicate that the behavioral challenges associated with SICS may be more robust than laboratory studies have indicated.     

Strike-induced chemosensory searching in old world vipers and new world pit vipers at San Diego Zoo

Rattlesnakes (Crotalus unicolor, C vegrandis) and Russell's vipers (Vipera russelli) at San Diego Zoo exhibited sustained high rates of tongue flicking after striking mice (Mus musculus) but not after seeing, smelling, and/or detecting thermal cues arising from mice. Called strike-induced chemosensory searching (SICS), this phenomenon contributes to poststrike trailing of envenomated prey. Because these zoo-raised snakes had always been offered dead rodents, and because these prey were usually ingested without first being struck, the present snakes had rarely exercised their innate predatory repertoire (ie, ambush tactics including striking, releasing, and trailing). Indeed, most specimens had never before struck a mouse and, hence, had never exhibited SICS. The occurrence of SICS in the present study clearly indicates that this important aspect of the predatory repertoire had not been degraded as a consequence of long-term captive husbandry.     

Discrimination of integumentary prey chemicals and strike-induced chemosensory searching in the ball python,Python regius

Experimental tests show that the ball python (Python regius) has the ability to discriminate prey chemicals from control substances by tongue-flicking and exhibits a poststrike elevation in tongue-flicking rate (PETF). Prey chemical discrimination was revealed by significantly higher number of tongue-flicks and tongue-flick attack score in response to integumental chemicals from mice than to cologne or distilled water and by a higher frequency of biting in response to prey than control chemicals. PETF was indicated by higher tongue-flicking rates after biting than in several control conditions. Concurrent movements of the body suggest the operation of strike-induced chemosensory searching (SICS). Ecological factors affecting responses to prey chemicals, including defensive behaviors and characteristics of foraging behavior related to reliance on different sensory modalities, are discussed. The presence of PETF and SICS in a henophidian snake and in scleroglossan lizards suggests that these behaviors are plesiomorphic in snakes.     

Prey chemical discrimination and strike-induced chemosensory searching in lizards: Their absence in a crotaphytid lizard (Crotaphytus collaris) and a proposal for research in zoos

Lizards in seleroglossan families of actively foraging carnivores and the herbivorous iguanids use the tongue to gather chemical samples to detect, identify, and locate food prior to attack, and to relocate lost food. In contrast, previously studied iguanian families other than Iguanidae lack lingually mediated prey chemical discrimination (PCD) and do not exhibit lingually mediated chemosensory searching behavior for bitten prey that has escaped or been lost (SICS = strike-induced chemosensory searching). In the present study, experimental tests showed that PCD and SICS are absent in Crotaphytus collaris, a member of the previously unstudied family of iguanian ambush foragers, Crotaphytidae. Available data suggest that in active foragers natural selection favors use of chemical cues to locate hidden prey, whereas in ambush foragers natural selection favors immobility to avoid detection by predators and SICS precludes simultaneous ambush. In most families the states of PCD and SICS are retained from the ancestors, but when foraging mode shifts, a change in chemosensory behavior appears to be induced. A proposal is made for a research program involving herpetologists at zoos. © 1996 Wiley-Liss, Inc.     

To forage,mate, or thermoregulate: Influence of resource manipulation on male rattlesnake behavior

Male animals should preferentially allocate their time to performing activities that promote enhancing reproductive opportunity, but the need to acquire resources for growth and survival may compete with those behaviors in the short term. Thus, behaviors which require differing movement patterns such as ambushing prey and actively searching for mates can be mutually exclusive. Consequently, males that succeed at foraging could invest greater time and energy into mate searching. We radio‐tracked sixteen male massasauga rattlesnakes (Sistrurus catenatus) and supplemented the diets of half the snakes with mice across an active season. We tested the predictions that reduced foraging needs would allow fed snakes to move (i.e., mate search) more, but that they would consequently be stationary to thermoregulate less, than unfed controls. Contrary to our first prediction, we found no evidence that fed snakes altered their mate searching behavior compared to controls. However, we found controls maintained higher body temperatures than fed snakes during the breeding season, perhaps because fed snakes spent less time in exposed ambush sites. Fed snakes had higher body condition scores than controls when the breeding season ended. Our results suggest the potential costs incurred by devoting time to stationary foraging may be outweighed by the drive to increase mating opportunities. Such instances may be especially valuable for massasaugas and other temperate reptiles that can remain inactive for upwards of half their lives or longer in some cases, and for female rattlesnakes that generally exhibit biennial or more protracted reproductive cycles.     

Rattling Behavior of Prairie Rattlesnakes (Crotalus viridis viridis,Viperidae) in Relation to Sex,Reproductive Status,Body Size,and Body Temperature

We examined whether sex, reproductive status, body size, or body temperature of prairie rattlesnakes (Crotalus viridis viridis) was related to when snakes rattled in response to an approaching observer. We found that gravid females allowed significantly closer approaches than males, suggesting that females relied on crypsis to avoid predation, possibly because pregnancy constrained their locomotive ability. Smaller snakes allowed significantly closer approaches than did larger snakes. Smaller snakes may be more cryptic or slower, which may influence their waiting to rattle until the observer was close. Overall, we found no consistent relationship between the distance from the observer that a snake rattled and its body temperature. However, cooler gravid females allowed closer approaches by the observer than did warmer gravid females. In summary, reproductive status, body size, and body temperature appear to influence the costs and benefits of crypsis vs. active defense of rattlesnakes.     

Duration of strike-induced chemosensory searching in long-term captive rattlesnakes at national zoo,audubon zoo,and San Diego Zoo

Rattlesnakes typically strike and release adult rodent prey. Striking is followed by a sustained, high rate of tongue flicking that guides the snake to the envenomated, dead prey. Wild-caught rattlesnakes exhibited this chemosensory searching for about 2.5 h, and the present study demonstrated that long-term captive rattlesnakes (Crotalus atrox, C durissus, C horridus, C vegrandis, C unicolor) at three zoos did the same. Because these zoo-raised snakes had always been offered dead rodents and because the snakes had become accustomed to ingesting them without striking, the present snakes had rarely exercised their innate predatory repertoires. The duration of chemosensory searching in these snakes indicates that this important aspect of the predatory repertoire had not been degraded as a consequence of long-term captive husbandry.     

Post-bite Elevation in Tongue-flick Rate by Neonatal Garter Snakes (Thamnophis radix)

A post-biting elevation in tongue-flicking rate was demonstrated experimentally in neonatal, ingestively naive garter snakes (Thamnophis radix). That the snakes also exhibited apparent searching movements suggests that strike-induced chemosensory searching occurs in nonvenomous snakes lacking previous experience with food or prey chemicals. Two litters of neonates differed in numbers of tongue-flicks emitted, but had similar relative magnitudes of response across experimental conditions. The existence of post-bite elevation in tongue-flick rate (and presumably strike-induced chemosensory searching) argues for a genetic basis for these chemosensory behaviors in a nonvenomous species of snake, extending the recent finding that strike-induced chemosensory searching is fully developed in ingestively naive neonatal rattlesnakes. Possible patterns of evolution of post-bite elevation in tongue-flick rate, and the strike-release-trail strategy of highly venomous snakes are discussed.     

Causes and consequences of aggregation by neonatal tiger snakes (Notechis scutatus,Elapidae)

Although snakes traditionally have been regarded as asocial animals, recent studies have revealed complex interactions among neonatal snakes and their mothers. We noticed frequent aggregation by captive neonatal Australian elapids (tiger snakes, Notechis scutatus), and conducted simple experiments to clarify the proximate causation of, and potential consequences of, aggregative behaviour. Litters of neonates exhibited statistically significant aggregation (clustering) in empty containers, especially if the test area was subjected to rapid cooling. Aggregation was most pronounced inside shelter‐sites, and familiar shelters (i.e. containing scent cues from the litter) attracted snakes more than did novel (unscented) shelters. Snakes in larger aggregations cooled more slowly (reflecting their higher combined mass and thus, thermal inertia) and higher body temperatures facilitated neonatal locomotor performance, retreat‐site location and anti‐predator tactics. Plausibly, aggregation in neonatal tiger snakes (and other reptiles) functions to retard cooling rates, with the result that the young snakes are better able to evade or repel attacks by predators.     

Chemosensory Response of Desert Iguanas (Dipsosaurus dorsalis) to Skin Lipids from A Lizard-Eating Snake (Lampropeltis getula californiae)

Several species of lizards respond to chemicals from sympatric lizard‐eating snakes with increased tongue‐extrusion rates. These substances also elicit antipredator behavior indicating that they have important ecological functions and the resulting behavior can have serious implications for individual fitness of lizards. However, the source and type of snake chemical cues that elicit these behavioral changes in lizards have yet to be determined. We tested the ability of adult desert iguanas (Dipsosaurus dorsalis) to detect and identify a potential predator by exposing them to lipids extracted from shed snakeskins. Lipids were extracted from cast skins of a known lizard‐eating snake, the California kingsnake (Lampropeltis getula californiae), using chloroform and methanol. Test subjects were presented with skin lipids as well as clean, pungent, and chloroform controls on cotton‐tipped applicators in random order. Desert iguanas directed significantly more tongue extrusions toward applicators bearing snakeskin lipids when compared with controls. In addition, overall tongue‐extrusion frequency increased following exposure to lipids during the 5‐min trials. Desert iguanas clearly detected snakeskin lipids, but this stimulus failed to elicit changes in body posture and movement patterns previously observed in experiments using chemical cues from live snakes. Increased tongue flicking by lizards in response to snakeskin lipids may represent a generalized response to this class of chemicals. Additional potential sources of chemicals used in the detection of lizard‐eating snakes are discussed.     

Aging in snakes: Results of long-term captivity on rattlesnake (Crotalus viridis oreganus) predatory behavior

Conservation, scientific study, rehabilitation, and public education concerning animals often require or take advantage of captive individuals. The long-term effects of captivity may affect the success and strategies used in such programs. For reptiles in particular, little is known about the effects of long-term captivity. We compared the predatory behavior of the same eight Northern Pacific Rattlesnakes before and after 7 years in captivity. We found few changes in predatory behavior. Most changes were in the rate of tongue flicks before the strike and during recovery of prey; these changes seemed related to accommodation of the snakes to conditions of captivity. However, most aspects of rattlesnake predatory behavior remained unchanged, including the normal ability to target the prey accurately and kill it quickly. Although the snakes had spent over half their lives in captivity and reached a relatively old age, their ability to strike, dispatch, and relocate prey normally was relatively unaffected by captivity or by aging. © 1994 Wiley-Liss, Inc.     

Intrinsic and Extrinsic Factors Influence Expression of Defensive Behavior in Plains Hog‐Nosed Snakes (Heterodon nasicus)

Animals failing to deter predation are eaten. Among the many deterrents to predation, antipredator behaviors are perhaps the most variable, ranging from active (fight or flight) to passive (immobility). We assessed variation in the expression of a passive defensive behavior, death‐feigning, in Plains Hog‐nosed Snakes (Heterodon nasicus) and predicted that intrinsic and extrinsic factors would influence the duration of this behavior and the latency to its onset. We simulated predatory attacks on 27 snakes encountered in the field, and analyzed the behavioral responses of snakes as a function of differences among individuals (sex and size) and environmental factors (temperature and microhabitat). Larger snakes death‐feigned for longer durations than smaller ones; this relationship was stronger for female snakes than for males. Death feints were initiated sooner when snakes were encountered at higher temperatures. Extrinsic factors had a greater influence on latency to death‐feigning behavior, whereas intrinsic factors more strongly influenced its duration. Because our results involved wild snakes, they provide an improved, highly relevant understanding of individual and environmental factors that regulate the expression of immobile defensive behavior. Furthermore, additional hypotheses can now be proposed that address the evolution of defensive behaviors that leave animals prone to attack.     

Feeding ecology of North American gopher snakes (Pituophis catenifer, Colubridae)

Studies of food relations are important to our understanding of ecology at the individual, population and community levels. Detailed documentation of the diet of large‐bodied, widespread snakes allows us to assess size‐dependent and geographical variation in feeding preferences of gape‐limited predators. Furthermore, with knowledge of the food habits of sympatric taxa we can explore possible causes of interspecific differences in trophic niches. The feeding ecology of the North American gopher snake, Pituophis catenifer, was studied based on the stomach contents of more than 2600 preserved and free‐ranging specimens, and published and unpublished dietary records. Of 1066 items, mammals (797, 74.8%), birds (86, 8.1%), bird eggs (127, 11.9%), and lizards (35, 3.3%) were the most frequently eaten prey. Gopher snakes fed upon subterranean, nocturnal and diurnal prey. The serpents are primarily diurnal, but can also be active at night. Therefore, gopher snakes captured their victims by actively searching underground tunnel systems, retreat places and perching sites during the day, or by pursuing them or seizing them while they rested at night. Gopher snakes of all sizes preyed on mammals, but only individuals larger than 40 and 42 cm in snout–vent length took bird eggs and birds, respectively, possibly due to gape constraints in smaller serpents. Specimens that ate lizards were smaller than those that consumed mammals or birds. Gopher snakes raided nests regularly, as evidenced by the high frequency of nestling mammals and birds and avian eggs eaten. Most (332) P. catenifer contained single prey, but 95 animals contained 2–35 items. Of the 321 items for which direction of ingestion was determined, 284 (88.5%) were swallowed head‐first, 35 (10.9%) were ingested tail‐first, and two (0.6%) were taken sideways. Heavier gopher snakes took heavier prey, but heavier serpents ingested prey with smaller mass relative to snake mass, evidence that the lower limit of prey mass did not increase with snake mass. Specimens from the California Province and Arid Deserts (i.e. Mojave, Sonoran and Chihuahuan Deserts) took the largest proportion of lizards, whereas individuals from the Great Basin Desert consumed a higher percentage of mammals than serpents from other areas, and P. catenifer from the Great Plains ate a greater proportion of bird eggs. Differences in prey availability among biogeographical regions and unusual circumstances of particular gopher snake populations may account for these patterns. Gopher snakes have proportionally longer heads than broadly sympatric Rhinocheilus lecontei (long‐nosed snake), Charina bottae (rubber boa) and Lampropeltis zonata (California mountain kingsnake), which perhaps explains why, contrary to the case in P. catenifer, the smaller size classes of those three species do not eat mammals. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 77 , 165–183.     

Costs of infant‐carrying in the cotton‐top tamarin (Saguinus oedipus)

Infant‐carrying behavior among callitrichids seems to be a costly activity. Costs have been related to the physical efforts of carrying the weight of very heavy infants and to the resulting reduction in foraging efficiency. However, the costs of carrying in terms of the physical consequences for carriers have not previously been assessed. In this study, we have regarded weight loss in infant carriers as a measure of costs. We studied five families of cotton‐top tamarins (Saguinus oedipus) during the first 9 weeks following the birth of infants. Captive‐breeding conditions were required so that body weight could be measured frequently. To avoid inflicting undue stress on the subject animals, we used a noninvasive method for weighing the tamarins. Differences in carrying contribution were found amongst fathers and male and female helpers, with female helpers contributing less. We have found that carrying infants in the cotton‐top tamarins is an activity that produces a weight loss. Fathers and male helpers go through a maximal body weight loss. While carrying, the tamarins also decrease food intake. However, no relationship was found between contribution to carrying and feeding time or in energetic intake during feeding observations. Thus, it seems that a direct relation doesn't exist between the observations of feeding and weight loss. Fathers increase their contribution to carrying during mothers' periovulatory periods. In this period, male helpers and especially fathers go through a maximal body weight loss. We found body weight losses of up to 11.3% in one subadult male and 9.1percnt; in a father during the fifth week. No changes occurred in food intake in fathers or other male helpers during this period. During periovulatory periods, mothers carried less frequently but did increase their food intake. They gained weight from the second week after birth onward, especially during the periovulatory period. It seems that the infant‐carrying behavior of fathers and male helpers may contribute to the improvement of the mothers' physical condition after birth and therefore may support a consecutive pregnancy. Am. J. Primatol. 48:99–111, 1999. © 1999 Wiley‐Liss, Inc.     

Meal Size Effects on Antipredator Behavior of Hatchling Trinket Snakes, Elaphe helena

Current foraging models limit the decision‐making process of animals to the food searching and consuming phase. The post‐consummatory phase of feeding may influence optimal meal size for some species as a morphologic change often results from feeding. In snakes, a single prey item can lead to abrupt increases in body mass, thus influencing locomotor performance. Identifying factors affecting locomotor performance can help predict behaviors that should maximize an animal's chance of evading predators. Although many snakes ingest large percentages of their body mass, not much work has examined the post‐consummatory effects of ingesting bulky prey differing in relative mass. I examined the locomotor performance and antipredator tactics of hatchling trinket snakes (Elaphe helena) after subjecting snakes to mice prey varying by relative mass differences of 20–35%, 50–59% or 70–79% of an individual hatchling's body mass. Snakes in treatment groups were compared with snakes in a control group (0%). Meal size‐affected locomotor parameters such as burst speed, endurance, and endurance times for hatchlings that ingested 50–59% and 70–79% of their body mass (p < 0.001). Recent feeding also affected the types of antipredator modes employed. Hatchlings in the 0% and 20–35% treatments exhibited behaviors that were categorized as active and threatening, while hatchlings in the 50–59% and 70–79% treatments exhibited stationary, neutral, and cryptic behaviors. Although snakes may become more reclusive following a meal, this study demonstrates that relative prey mass affects the ability of hatchling trinket snakes to flee from a predator. In turn, these results suggest that the post‐consummatory effects of foraging should be considered in optimal foraging models for organisms that consume a substantial portion of their body mass during a single feeding.     

Snake Species Discrimination by Wild Bonnet Macaques (Macaca radiata)

Wild bonnet macaques (Macaca radiata) were studied in southern India to assess their ability to discriminate non‐venomous, venomous and predatory snakes. Realistic snake models were presented to eight troops of bonnet macaques at feeding stations and their behavior was video‐recorded 3 min before and 3 min after snake exposure. Snakes presented were: (1) venomous Indian cobra (Naja naja) displaying an open hood with ‘eyespots’; (2) venomous common Indian krait (Bungarus caeruleus); (3) non‐venomous green keelback (Macropisthodan plumbicolor); (4) non‐venomous rat snake (Ptyas mucosus); and (5) Indian python (Python molurus) which preys on macaques. Latencies to detect and react to the snakes were evaluated to determine initial responsiveness. Longer‐term assessment was measured as the percentage of time individuals looked at the snakes and monitored the activity of nearby individuals before and after snake detection. All snake models engendered caution and maintenance of a safe distance. Alarm calling occurred only during python presentations. The cobra engendered a startle response or running in the largest percentage of individuals after its detection, whereas the rat snake and python elicited bipedal standing or ambulating to monitor the snakes. We also examined the influence of age on snake recognition. Juveniles and subadults looked at the cobra, krait, and python for a larger percentage of time than adults did; albeit, adults looked at the python substantially longer than at the other snakes. Age differences in behavior suggest that, with the exception of the python, repeated experience with snakes in the wild moderates excitability, consistent with the likely threat of envenomation.     

Black rhinoceros (Diceros bicornis) in U.S. zoos: II. behavior,breeding success,and mortality in relation to housing facilities

The captive population of black rhinoceros (Diceros bicornis) is not self‐sustaining. The reasons for suboptimal reproduction and high mortality need to be investigated. This can only be achieved by cross‐institutional analyses of environments, behavior, and performance. In this study, we collected data on 23 zoos with black rhinoceros to compare zoo environments with reproductive success, mortality, and behavior. Institutional variation was characterized by enclosure area, percentage of walls around enclosure perimeter, percentage of public access along enclosure perimeter, climate, noise level, number of years zoo has maintained black rhinoceros, frequency of chlorine use, and number of male and female black rhinoceros at a zoo simultaneously. Birth and death rates for each institution were calculated from studbook records. We found that the breeding success of a zoo since 1973 correlated positively with enclosure area, and zoos with two or more females had a lower reproductive rate than zoos with only one female. Females residing during their pre‐reproductive years at a zoo with another reproductive female gave birth for the first time on average 3 years later than sole females. Mortality since 1973 correlated positively with percentage of public access. In Part I, we developed behavior profiles of 29.31 individual black rhinoceros from keeper ratings. Scores for males on the behavior trait Fear also correlated positively to percentage of public access, and we suggest that this aspect of black rhinoceros exhibits is a stressor for this species, especially the males. We found that different aspects of captive environments are associated with male and female black rhinoceros behavior. Male scores on the behavior trait dominant were higher in smaller enclosures, and female scores for a group of behaviors suggesting agitation (chasing/stereotypy/mouthing) were positively correlated with percentage of walls in their enclosure. These two behavior traits were found in Part I to be negatively correlated with the breeding success of an individual male or female. We re‐surveyed the behavior and husbandry of 29 black rhinoceros pairs in zoos 2 years after the original data were collected. The re‐survey confirmed that compatible black rhinoceros pairs are those with assertive females and submissive males, and that enclosure area and a low percentage of concrete walls around the enclosure are positive predictors of a pair's reproductive success. We conclude that temperament traits of individuals and characteristics of their captive environments both have an impact on a pair's breeding success. Our study demonstrates that cross‐institutional comparisons of zoo facilities, when integrated with behavioral assessments of individual animals, are a valuable tool for investigating potential causes of poor reproduction and well‐being in zoo animals. Zoo Biol 18:35–52, 1999. © 1999 Wiley‐Liss, Inc.     

Sedentary behavior, recreational physical activity, and 7-year weight gain among postmenopausal U.S. women

Objective: To assess the relationship among recreational physical activity (PA), non‐occupational sedentary behavior, and 7‐year weight gain among postmenopausal U.S. women 40 to 69 years old. Research Methods and Procedures: In 1992 and 1999, 18,583 healthy female participants from the Cancer Prevention Study II Nutrition Cohort completed questionnaires on anthropometric characteristics and lifestyle factors. The associations between recreational PA [in metabolic equivalent (MET) hours per week] and non‐occupational sedentary behavior (in hours per day) at baseline and risk for 7‐year weight gain (5 to 9 or ≥10 vs. ±4 pounds) were assessed using multivariate logistic regression analysis. Results: Neither PA nor sedentary behavior was associated with a 5‐ to 9‐pound weight gain. Among women who were not overweight at baseline (BMI <25.0), the odds of ≥10‐pound weight gain were 12% lower (odds ratio, 0.88; 95% confidence interval, 0.77 to 0.99) for those in the highest category of recreational PA (≥18 MET h/wk) compared with >0 to <4 MET h/wk; odds were 47% higher (odds ratio, 1.47; 95% confidence interval, 1.21 to 1.79) for non‐overweight women who reported ≥6 h/d of non‐occupational sedentary behavior compared with <3 h/d. Neither PA nor sedentary behavior were associated with risk of ≥10‐pound weight gain weight among women who were overweight at baseline (BMI ≥25.0). Discussion: Both recreational PA and non‐occupational sedentary behavior independently predicted risk of ≥10‐pound weight gain among postmenopausal women who were not overweight at baseline. Public health messages to prevent weight gain among normal‐weight postmenopausal women may need to focus on decreasing time spent in sedentary behaviors and increasing the amount of time spent on PA.     

Scale variation in a laboratory colony of amelanistic diamondback rattlesnakes (Crotalus atrox)

Inbreeding for 6 generations has produced a strain of amelanistic western diamondback rattlesnakes (Crotalus atrox) with extremely variable scalation. Forty-four siblings varying from virtually no body scalation to normal scalation have been produced in the latest generation. Two of the 3 most extreme “scaleless” snakes were stillborn; the third was maintained for > 1 year. Two of 7 snakes with greatly reduced head and body scales have died; however, the remaining 5 are being maintained and appear to be growing and healthy at 5 or 6 years of age. All snakes with reduced body scales have abnormal ventral scutes. Fifteen snakes with predominantly normal body scales have anomalous head scales, head scale patterns, and ventral scutes. One snake has predominantly normal scalation except for aberrant ventrals. A total of 18 Generation VI snakes have been classified as “normal,” although all snakes were not closely examined before disposition. Nine of the more normally scaled generation VI snakes are also being maintained in the laboratory. It is difficult to separate the genetic and environmental components of these phenotypes with existing information; however, it seems apparent that more than a single locus is involved. © 1994 Wiley-Liss, Inc.     

Mitochondrial phylogeography,contact zones and taxonomy of grass snakes (Natrix natrix,N. megalocephala)

Grass snakes (Natrix natrix) represent one of the most widely distributed snake species of the Palaearctic region, ranging from the North African Maghreb region and the Iberian Peninsula through most of Europe and western Asia eastward to the region of Lake Baikal in Central Asia. Within N. natrix, up to 14 distinct subspecies are regarded as valid. In addition, some authors recognize big‐headed grass snakes from western Transcaucasia as a distinct species, N. megalocephala. Based on phylogenetic analyses of a 1984‐bp‐long alignment of mtDNA sequences (ND4+tRNAs, cyt b) of 410 grass snakes, a nearly range‐wide phylogeography is presented for both species. Within N. natrix, 16 terminal mitochondrial clades were identified, most of which conflict with morphologically defined subspecies. These 16 clades correspond to three more inclusive clades from (i) the Iberian Peninsula plus North Africa, (ii) East Europe and Asia and (iii) West Europe including Corso‐Sardinia, the Apennine Peninsula and Sicily. Hypotheses regarding glacial refugia and postglacial range expansions are presented. Refugia were most likely located in each of the southern European peninsulas, Corso‐Sardinia, North Africa, Anatolia and the neighbouring Near and Middle East, where the greatest extant genetic diversity occurs. Multiple distinct microrefugia are inferred for continental Italy plus Sicily, the Balkan Peninsula, Anatolia and the Near and Middle East. Holocene range expansions led to the colonization of more northerly regions and the formation of secondary contact zones. Western Europe was invaded from a refuge within southern France, while Central Europe was reached by two distinct range expansions from the Balkan Peninsula. In Central Europe, there are two contact zones of three distinct mitochondrial clades, and one of these contact zones was theretofore completely unknown. Another contact zone is hypothesized for Eastern Europe, which was colonized, like north‐western Asia, from the Caucasus region. Further contact zones were identified for southern Italy, the Balkans and Transcaucasia. In agreement with previous studies using morphological characters and allozymes, there is no evidence for the distinctiveness of N. megalocephala. Therefore, N. megalocephala is synonymized with N. natrix.