Life-History and Spatial Determinants of Somatic Growth Dynamics in Komodo Dragon Populations

Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world’s largest lizard the Komodo dragon (Varanus komodoensis). The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs) and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species.     

Effects of human activities on Komodo dragons in Komodo National Park

Understanding how threatened wildlife can coexist with humans over the long term is a central issue in conservation and wildlife management. Komodo National Park in Eastern Indonesia, harbors the largest extant populations of the endemic Komodo dragon (Varanus komodoensis). Consistent with global trends, this species is expected to be increasingly exposed to human activities and in particular growing ecotourism activities. Here we comprehensively evaluated how human activities affected individual and population level attributes of Komodo dragons. We compared Komodo dragons phenotypic (behaviour, body size, and body condition) and demographic (age structure, sex ratio, survival, and density) responses to variation in human activities across national park. Komodo dragons were found to exhibit pronounced responses to high human activity level relative to sites with low and negligible human activities. Komodo dragons exposed to ecotourism exhibited significantly less wariness, larger body mass, better body condition, and higher survival. These results are entirely consistent with ecotourism activities that provided Komodo dragons with long-term and substantial nutritional subsidies as a consequence of feeding and human food refuse. However, we also noted the potential negative consequences of altered behaviour and adult-biased populations in ecotourism areas which may influence demographic processes through intraspecific competition or predation. To address this issue, we recommend that three management strategies to be implemented in future include: (1) removal of human-mediated nutritional subsidies, (2) alternative ecotourism, and (3) spatial regulation of ecotourism. Furthermore, we advocate the development of approaches to achieve a socio–ecological sustainability that benefits both people and wildlife conservation.     

Evaluating environmental,demographic and genetic effects on population‐level survival in an island endemic

The population dynamics of island species are considered particularly sensitive to variation in environmental, demographic and/or genetic processes. However, few studies have attempted to evaluate the relative importance of these processes for key vital rates in island endemics. We integrated the results of long‐term capture–mark–recapture analysis, prey surveys, habitat quality assessments and molecular analysis to determine the causes of variation in the survival rates of Komodo dragons Varanus komodoensis at 10 sites on four islands in Komodo National Park, Indonesia. Using open population capture–mark–recapture methods, we ranked competing models that considered environmental, ecological, genetic and demographic effects on site‐specific Komodo dragon survival rates. Site‐specific survival rates ranged from 0.49 (95% CI: 0.33–0.68) to 0.92 (0.79–0.97) in the 10 study sites. The three highest‐ranked models (i.e. ΔQAIC_c < 2) explained ～70% of variation in Komodo dragon survival rates and identified interactions between inbreeding coefficients, prey biomass density and habitat quality as important explanatory variables. There was evidence of additive effects from ecological and genetic (e.g. inbreeding) processes affecting Komodo dragon survival rates. Our results indicate that maintaining high ungulate prey biomass and habitat quality would enhance the persistence of Komodo dragon populations. Assisted gene flow may also increase the genetic and demographic viability of the smaller Komodo dragon populations.     

Genetic structure and gene flow among Komodo dragon populations inferredby microsatellite loci analysis

A general concern for the conservation of endangered species is the maintenance of genetic variation within populations, particularly when they become isolated and reduced in size. Estimates of gene flow and effective population size are therefore important for any conservation initiative directed to the long-term persistence of a species in its natural habitat. In the present study, 10 microsatellite loci were used to assess the level of genetic variability among populations of the Komodo dragon Varanus komodoensis. Effective population size was calculated and gene flow estimates were compared with palaeogeographic data in order to assess the degree of vulnerability of four island populations. Rinca and Flores, currently separated by an isthmus of about 200 m, retained a high level of genetic diversity and showed a high degree of genetic similarity, with gene flow values close to one migrant per generation. The island of Komodo showed by far the highest levels of genetic divergence, and its allelic distinctiveness was considered of great importance in the maintenance of genetic variability within the species. A lack of distinct alleles and low levels of gene flow and genetic variability were found for the small population of Gili Motang island, which was identified as vulnerable to stochastic threats. Our results are potentially important for both the short- and long-term management of the Komodo dragon, and are critical in view of future re-introduction or augmentation in areas where the species is now extinct or depleted.     

Body temperature and thermoregulation of Komodo dragons in the field

Komodo dragons from hatchlings (≈0.1 kg) to adults (≤80 kg) express the full magnitude of varanid species size distributions. We found that all size groups of dragons regulated a similar preferred body temperature by exploiting a heterogeneous thermal environment within savanna, forest and mangrove habitats. All dragons studied, regardless of size, were able to regulate a daytime active body temperature within the range 34–35.6 °C for 5.1–5.6 h/day. The index of effectiveness of thermoregulation (a numerical rating of thermoregulatory activity) was not different among size groups of dragons. However, the index of closeness of thermoregulation, which rates the variability of body temperature, suggests a greater precision for regulating a preferred body temperature for medium compared to small and large dragons. Reference copper cylinders simulating small, medium and large Komodo dragons heated and cooled at the same rate, whereas actual dragons of all size groups heated faster than they cooled. Larger dragons heated and cooled more slowly than smaller ones. The mean operative environmental temperatures of copper cylinders representing medium sized dragons were 42.5, 32.0 and 29.4° C for savannah, forest and mangrove habitats, respectively. The index for average thermal quality of a habitat as measured by the absolute difference between operative environmental temperature and the dragon’s thermal range suggests the forest habitat offers the highest thermal quality to dragons and the savannah the lowest. The percent of total daytime that the operative environmental temperature was within the central 50% of the body temperatures selected by dragons in a thermal gradient (Phillips, 1984) was 45%, 15%, and 9% for forest, mangrove and savannah, respectively. Forest habitat offers the most suitable thermal environment and provides the greatest number of hours with conditions falling within the dragon’s thermal activity zone.     

Aerobic salivary bacteria in wild and captive Komodo dragons

During the months of November 1996, August 1997, and March 1998, saliva and plasma samples were collected for isolation of aerobic bacteria from 26 wild and 13 captive Komodo dragons (Varanus komodoensis). Twenty-eight Gram-negative and 29 Gram-positive species of bacteria were isolated from the saliva of the 39 Komodo dragons. A greater number of wild than captive dragons were positive for both Gram-negative and Gram-positive bacteria. The average number of bacterial species within the saliva of wild dragons was 46% greater than for captive dragons. While Escherichia coli was the most common bacterium isolated from the saliva of wild dragons, this species was not present in captive dragons. The most common bacteria isolated from the saliva of captive dragons were Staphylococcus capitis and Staphylococcus capitis and Staphylococcus caseolyticus, neither of which were found in wild dragons. High mortality was seen among mice injected with saliva from wild dragons and the only bacterium isolated from the blood of dying mice was Pasteurella multocida. A competitive inhibition enzyme-linked immunosorbent assay revealed the presence of anti-Pasteurella antibody in the plasma of Komodo dragons. Four species of bacteria isolated from dragon saliva showed resistance to one or more of 16 antimicrobics tested. The wide variety of bacteria demonstrated in the saliva of the Komodo dragon in this study, at least one species of which was highly lethal in mice and 54 species of which are known pathogens, support the observation that wounds inflicted by this animal are often associated with sepsis and subsequent bacteremia in prey animals.     

Distribution, seasonal use, and predation of incubation mounds of Orange-footed Scrubfowl on Komodo Island, Indonesia

ABSTRACT.   Megapodes are unique in using only heat from the environment, rather than body heat, to incubate their eggs as well as the precocious independence of their chicks on hatching. Of 22 recognized species of megapodes, 9 are listed as threatened due to factors including habitat loss and fragmentation, and predation on eggs and chicks. Orange-footed Scrubfowl ( Megapodius reinwardt ) are conspicuous components of the Oriental/Austral avifauna that inhabit the monsoon forests of the Lesser Sunda chain of islands in Indonesia. We examined the abundance, patterns of distribution, physical characteristics, seasonal activity, and predation risk of incubation mounds of Orange-footed Scrubfowl on Komodo Island in eastern Indonesia. We surveyed 13 valleys on Komodo Island from April 2002 to January 2005 and located 113 tended and 107 untended incubation mounds. Densities of scrubfowl mounds in our study were similar to that reported by investigators during the 1970s, suggesting little change in the scrubfowl population since then. Most scrubfowl mounds were on sandy or loamy soils in open monsoon forest with little overhead shade, and placement of mounds in such areas may ensure adequate temperatures for egg incubation. Although some mounds were tended during all months, mound use peaked during the late wet season in March. During the dry season (April–November), only a few mounds were tended. Komodo dragons ( Varanus komodoensis ) and wild pigs ( Sus scrofa ) were the primary predators of scrubfowl eggs, with no indication of egg predation by humans. The valley with the largest number of untended mounds in our study also had the largest number of active Komodo dragon nests. This suggests an effect of Komodo dragons on scrubfowl numbers, but additional study is needed.     

Blood values in wild and captive Komodo dragons (Varanus komodoensis)

The Komodo dragon (Varanus komodoensis) is the largest living lizard and occupies a range smaller than that of any other large carnivore in the world. Samples from 33 free-ranging animals at five localities in Komodo National Park, Indonesia were evaluated to assess underlying health problems. To build a comparative database, samples from 44 Komodo dragons in both Indonesian and U.S. zoos were also analyzed. Tests performed included complete blood counts, clinical chemistry profiles, vitamin A, D(3), and E analyses, mineral levels, and screening for chlorinated pesticides or other toxins in wild specimens. Blood samples from wild dragons were positive for hemogregarines, whereas captive specimens were all negative. Total white blood cell counts were consistently higher in captive Komodo dragons than in wild specimens. Reference intervals were established for some chemistry analytes, and values obtained from different groups were compared. Vitamin A and E ranges were established. Vitamin D(3) levels were significantly different in Komodo dragons kept in captive, indoor exhibits versus those with daily ultraviolet-B exposure, whether captive or wild specimens. Corrective measures such as ultraviolet-permeable skylights, direct sunlight exposure, and self-ballasted mercury vapor ultraviolet lamps increased vitamin D(3) concentrations in four dragons to levels comparable with wild specimens. Toxicology results were negative except for background-level chlorinated pesticide residues. The results indicate no notable medical, nutritional, or toxic problems in the wild Komodo dragon population. Problems in captive specimens may relate to, and can be corrected by, husbandry measures such as regular ultraviolet-B exposure. Zoo Biol 19:495-509, 2000. Copyright 2000 Wiley-Liss, Inc.     

Body size in the Eurasian lynx in Sweden: dependence on prey availability

The Eurasian lynx (Lynx lynx) is a common predator of both roe deer (Capreolus capreolus) and reindeer (Rangifer tarandus) in Sweden. We investigated the influence of prey availability, latitude, sex, and age on body size and body mass variation of the Eurasian lynx in Sweden, using data from 243 specimens whose locality of capture, year of capture, sex, and age were known. We found that both body size and body mass of the lynx in Sweden are mainly affected by the lynx sex and age but also by the availability of prey during the first year of life. Body size and body mass of lynx as well as the density of roe deer increased from Central Sweden to South. Furthermore, body size and body mass of lynx increased from Central Sweden to North (i.e. within the reindeer husbandry area). Lynx body size was slightly smaller within the reindeer husbandry area (approximately north of latitudes 62°–63°N) compared to outside, probably because reindeer are more difficult prey to hunt, as well as being migratory and thus an unpredictable prey for the Eurasian lynx compared to the non-migratory roe deer. Our results support a growing body of evidence showing that food availability at growth has a major effect on body size of animals.     

蝘蜓头、体大小的两性异形和雌体繁殖

报道了蜓 (Sphenomorphusindicus)头、体大小的两性异形和雌性繁殖。性成熟雌体大于雄体。雄性成体头长大于雌性成体 ,但头宽与雌性成体无显著差异。初生幼仔的头长和头宽无两性差异。雄性幼体头长和头宽大于雌性幼体。设置SVL恒定时 ,雄性幼体和雄性成体的头长和头宽无显著差异 ,雌性幼体的头长和头宽大于雌性成体。初生幼仔具有相对较大的头部。产仔雌体的最小SVL为 6 7 7mm ,大于此SVL的雌体均年产单窝仔。平均窝仔数、窝仔重和幼仔重分别为 7 2 ( 3～ 11)、 3 34( 1 30～ 5 19)和 0 48( 0 36～ 0 5 8)g。用卵黄沉积卵巢卵和输卵管计数的窝仔数比用幼仔计数的窝仔数多约 1 0个后代。幼仔体重与雌体SVL无关。相对窝仔重与雌体SVL边缘性地呈正相关。窝仔数、窝仔重与雌体SVL呈正相关 ,幼仔体重与窝仔数呈负相关。窝仔数与雌体状态无关。     

Body Size Evolution in Insular Speckled Rattlesnakes (Viperidae: Crotalus mitchellii)

Background

Speckled rattlesnakes (Crotalus mitchellii) inhabit multiple islands off the coast of Baja California, Mexico. Two of the 14 known insular populations have been recognized as subspecies based primarily on body size divergence from putative mainland ancestral populations; however, a survey of body size variation from other islands occupied by these snakes has not been previously reported. We examined body size variation between island and mainland speckled rattlesnakes, and the relationship between body size and various island physical variables among 12 island populations. We also examined relative head size among giant, dwarfed, and mainland speckled rattlesnakes to determine whether allometric differences conformed to predictions of gape size (and indirectly body size) evolving in response to shifts in prey size.

Methodology/Principal Findings

Insular speckled rattlesnakes show considerable variation in body size when compared to mainland source subspecies. In addition to previously known instances of gigantism on Ángel de la Guarda and dwarfism on El Muerto, various degrees of body size decrease have occurred frequently in this taxon, with dwarfed rattlesnakes occurring mostly on small, recently isolated, land-bridge islands. Regression models using the Akaike information criterion (AIC) showed that mean SVL of insular populations was most strongly correlated with island area, suggesting the influence of selection for different body size optima for islands of different size. Allometric differences in head size of giant and dwarf rattlesnakes revealed patterns consistent with shifts to larger and smaller prey, respectively.

Conclusions/Significance

Our data provide the first example of a clear relationship between body size and island area in a squamate reptile species; among vertebrates this pattern has been previously documented in few insular mammals. This finding suggests that selection for body size is influenced by changes in community dynamics that are related to graded differences in area over what are otherwise similar bioclimatic conditions. We hypothesize that in this system shifts to larger prey, episodic saturation and depression of primary prey density, and predator release may have led to insular gigantism, and that shifts to smaller prey and increased reproductive efficiency in the presence of intense intraspecific competition may have led to insular dwarfism.     

青海沙蜥的两性异型和雌性繁殖

作者研究了青海沙蜥(Phrynocephalus vlangalii)形态特征的两性异形和雌体繁殖特征。蜥蜴于2005年5月初捕自西宁以西约150km的倒淌河,被检形态特征包括体色、体长、腹长、尾长、头长和头宽,新排卵雌体维持在实验室梯度热环境中直至产仔。成体两性异形显著,而性未成熟个体缺乏两性异形。最大的成年雄体和雌体分别为70.2mmSVL(snout-vent length)和82.8mmSVL。雄性成体具有相对较大的头长、头宽和尾长,雌性成体SVL大于雄体且具有相对较大的腹长。对4个形态特征进行主成分分析(特征值≥0.5)区分出2个主成分,共解释83.9%的两性相关形态特征的变异。去除SVL差异的影响后,尾长、头长和头宽在第一主成分有较高的正负载系数(解释57.8%的变异),腹长在第二主成分有较高的负负载系数(解释26.1%的变异)。实验室梯度热环境下的雌体于6月下旬至7月中旬产单窝、2-6个后代。窝仔数和窝仔重与母体SVL呈正相关,幼仔重与母体SVL无关。未在青海沙蜥中检测到后代数量与大小之间的权衡。     

Predators in natural fragments: foraging ecology of wolves in British Columbia's central and north coast archipelago

Aim Predator–prey dynamics in fragmented areas may be influenced by spatial features of the landscape. Although little is known about these processes, an increasingly fragmented planet underscores the urgency to predict its consequences. Accordingly, our aim was to examine foraging behaviour of an apex mammalian predator, the wolf (Canis lupus), in an archipelago environment. Location Mainland and adjacent archipelago of British Columbia, Canada; a largely pristine and naturally fragmented landscape with islands of variable size and isolation. Methods We sampled 30 mainland watersheds and 29 islands for wolf faeces in summers 2000 and 2001 and identified prey remains. We examined broad geographical patterns and detailed biogeographical variables (area and isolation metrics) as they relate to prey consumed. For island data, we used Akaike Information Criteria to guide generalized linear regression model selection to predict probability of black‐tailed deer (main prey; Odocoileus hemionus) in faeces. Results Black‐tailed deer was the most common item in occurrence per faeces (63%) and occurrence per item (53%) indices, representing about 63% of mammalian biomass. Wolves consumed more deer on islands near the mainland (65% occurrence per item) than on the mainland (39%) and outer islands (45%), where other ungulates (mainland only) and small mammals replaced deer. On islands, the probability of detecting deer was influenced primarily by island distance to mainland (not by area or inter‐landmass distance), suggesting limited recolonization by deer from source populations as a causal mechanism. Main conclusions Although sampling was limited in time, consistent patterns among islands suggest that population dynamics in isolated fragments are less stable and can result in depletion of prey. This may have important implications in understanding predator–prey communities in isolation, debate regarding wolf–deer systems and logging in temperate rain forests, and reserve design.     

Evaluation of three field monitoring-density estimation protocols and their relevance to Komodo dragon conservation

Finding practical ways to robustly estimate abundance or density trends in threatened species is a key facet for effective conservation management. Further identifying less expensive monitoring methods that provide adequate data for robust population density estimates can facilitate increased investment into other conservation initiatives needed for species recovery. Here we evaluated and compared inference-and cost-effectiveness criteria for three field monitoring-density estimation protocols to improve conservation activities for the threatened Komodo dragon (Varanus komodoensis). We undertook line-transect counts, cage trapping and camera monitoring surveys for Komodo dragons at 11 sites within protected areas in Eastern Indonesia to collect data to estimate density using distance sampling methods or the Royle–Nichols abundance induced heterogeneity model. Distance sampling estimates were considered poor due to large confidence intervals, a high coefficient of variation and that false absences were obtained in 45 % of sites where other monitoring methods detected lizards present. The Royle–Nichols model using presence/absence data obtained from cage trapping and camera monitoring produced highly correlated density estimates, obtained similar measures of precision and recorded no false absences in data collation. However because costs associated with camera monitoring were considerably less than cage trapping methods, albeit marginally more expensive than distance sampling, better inference from this method is advocated for ongoing population monitoring of Komodo dragons. Further the cost-savings achieved by adopting this field monitoring method could facilitate increased expenditure on alternative management strategies that could help address current declines in two Komodo dragon populations.     

Ontogenetic differences in the spatial ecology of immature Komodo dragons

The early life-history stages of reptiles are extremely important to an individual's fitness, but in an ecological sense, among the most difficult to observe. Here, we used radio-tracking techniques to describe the differences in movement patterns, habitat use and home range between hatchling and juvenile Komodo dragons Varanus komodoensis on Komodo Island, Indonesia. The movement of hatchlings from their nests was largely linear and suggested a natal dispersal event. The movement patterns of juvenile Komodo dragons exhibited a greater spatial overlap than hatchlings, indicating greater site fidelity and thus use of a more defined activity area. The rates of daily movement were significantly less for hatchlings compared with juvenile dragons. The activity areas of hatchlings were significantly smaller than juvenile dragons. Both age classes preferred utilizing dry monsoon forest compared with other habitat types. Hatchlings were predominantly arboreal compared with juveniles and the degree of arboreal activity was strongly correlated with an individual's size. These distinct differences in spatial ecology between immature life-history stages suggest that different selection pressures may affect different size classes of Komodo dragons.     

Evolution of biometric and life‐history traits in lizards (Gallotia) from the Canary Islands

The aim was to study as to how biometric and life‐history traits of endemic lacertids in the Canary Islands (genus Gallotia) may have evolved, and possible factors affecting the diversification process of this taxon on successively appearing islands have been deduced. To that end, comparative analyses of sexual dimorphism and scaling of different body, head and life‐history traits to body size in 10 species/subspecies of Gallotia have been carried out. Both Felsenstein's independent contrasts and Huey and Bennett's ‘minimum evolution’ analyses show that male and female snout‐vent length (SVL) changed proportionally (sexual size dimorphism not changing with body size) throughout the evolution of these lizards and all within‐sex biometric traits have changed proportionally to SVL. Life‐history traits (size at sexual maturity, clutch size, hatchling SVL and mass, and life span) are highly correlated with adult female body size, the first two being the only traits with a positive allometry to female SVL. These results, together with the finding that the slope of hatchling SVL to female SVL regression was lower than that of SVL at maturity to female SVL, indicates that larger females reach maturity at a larger size, have larger clutches and, at the same time, have relatively smaller hatchlings than smaller females. There was no significant correlation between any pair of life‐history traits after statistically removing the effect of body size. As most traits changed proportionally to SVL, the major evolutionary change has been that of body size (a ca. threefold change between the largest and the smallest species), that is suggested to be the effect of variable ecological conditions faced by founder lizards in each island.     

Summer predation rates on ungulate prey by a large keystone predator: how many ungulates does a large predator kill?

Estimates of predation rates by large predators can provide valuable information on their potential impact on their ungulate prey populations. This is especially the case for pumas Puma concolor and its main prey, mule deer Odocoileus hemionus . However, only limited information on predation rates of pumas exist where mule deer are the only ungulate prey available. I used VHF telemetry data collected over 24-h monitoring sessions and once daily over consecutive days to derive two independent estimates of puma predation rates on mule deer where they were the only large prey available. For the 24-h data, I had 48 time blocks on female pumas with kittens, 43 blocks on females without kittens and 30 blocks on males. For the daily consecutive data, the average number of consecutive days followed was 51.5±4.2 days. There were data on five female pumas with kittens, five pregnant females and nine females without kittens. Predation rates over an average month of 30 days from the 24-h monitoring sessions were 2.0 mule deer per puma month for males (15.1 days per kill), 2.1 mule deer per puma month (14.3 days per kill) for females without kittens and 2.5 mule deer per puma month (12.0 days per kill) for pregnant females and females with kittens. For the consecutive daily data, females without kittens had an estimated predation rate of 2.1±0.14 mule deer per puma month (14.9±0.90 days per kill). Pregnant and females with kittens had predation rates of 2.7±0.18 and 2.6±0.21 mule deer per puma month, respectively (11.4±0.72 and 12.0±1.1 days per kill, respectively). Predation rates estimated in this study compared with those estimated by energetic demand for pumas in the study area but were lower than other field derived estimates. These data help increase our understanding of predation impacts of large predators on their prey.     

Reproductive ecology of red-chinned lizards (Sceloporus undulatus erythrocheilus) in Southcentral Colorado: comparisons with other populations of a wide-ranging species

Summary We studied the reproductive ecology of a population of Sceloporus undulatus erythrocheilus near Walsenburg, CO during the summers of 1987–1990. Reproductive activity commences soon after emergence in early May and continues until the middle of July. Females mature in their second year following hatching at an age of 20–21 months and a size of 60–63 mm snout-vent length (SVL). Two clutches, averaging10.9 eggs, are produced per year. Larger females produce larger clutches with an increase of one egg per 3 mm SVL. Average SVL of females was 71 mm. Eggs are reasonably large (0.32 g) and relative clutch mass was the largest reported for the species (34% of body mass). A principal component analysis was used to examine relationships among reproductive characters in 12 populations of Sceloporus undulatus. The analysis suggested that patterns of reproduction in this wide-ranging species result from several factors reflecting both adaptive and phylogenetic sources of variation.     

Adaptive variation in head size in Vipera berus L. populations

To prove that predators are morphologically adapted to the size of their prey one has to demonstrate that the morphological variation in the trophic apparatus is related to the prey size distribution and that the variation in the trait has some effect on individual fitness. I have studied geographic variation in relative head length (RHL) of adders, Vipera berus , on the Swedish mainland and on groups of islands in the Baltic Sea, and the relationship between RHL and physical condition, a character related to fitness. I also examined the relationship between RHL and sex and colour morph. Relative head length of adders was smallest on the mainland and increased on the islands with increasing body size of the main prey, Microtus agrestis , suggesting stabilizing selection for head size within each population. There was no difference in RHL between sexes or colour morphs. However, physical condition was positively correlated with RHL, indicating directional selection for larger heads. The observed pattern is interpreted as an evolutionary response to the geographic variation in body size of the main prey species and the smaller number of alternative prey species available on islands.     

Tick burden on European roe deer (<Emphasis Type="Italic">Capreolus capreolus</Emphasis>)

In our study we assessed the tick burden on roe deer (Capreolus capreolus L.) in relation to age, physical condition, sex, deer density and season. The main objective was to find predictive parameters for tick burden. In September 2007, May, July, and September 2008, and in May and July 2009 we collected ticks on 142 culled roe deer from nine forest departments in Southern Hesse, Germany. To correlate tick burden and deer density we estimated deer density using line transect sampling that accounts for different detectability in March 2008 and 2009, respectively. We collected more than 8,600 ticks from roe deer heads and necks, 92.6% of which were Ixodes spp., 7.4% Dermacentor spp. Among Ixodes, 3.3% were larvae, 50.5% nymphs, 34.8% females and 11.4% males, with significant seasonal deviation. Total tick infestation was high, with considerable individual variation (from 0 to 270 ticks/deer). Adult tick burden was positively correlated with roe deer body indices (body mass, age, hind foot length). Significantly more nymphs were found on deer from forest departments with high roe deer density indices, indicating a positive correlation with deer abundance. Overall, tick burden was highly variable. Seasonality and large scale spatial characteristics appeared to be the most important factors affecting tick burden on roe deer.