Subsistence hunting and commercial exploitation directly influence wildlife populations in many regions of Central and South America. Where prey populations are exploited, the foraging ecology of top-level predators can be effected negatively. This study assessed the food habits and prey selection of jaguar Panthera onca and puma Puma concolor within hunted and non-hunted segments of the Maya Biosphere Reserve (MBR), Guatemala. Food habits were determined from analysis of 76 jaguar and 145 puma scats collected within hunted and non-hunted areas of the MBR from February 2000 to August 2001. Diets of jaguar and puma were compared (1) within species between areas with and without hunting to evaluate effects of subsistence hunting, and (2) between species to evaluate resource partitioning between these sympatric carnivores. Origin of predator scats was determined from mitochondrial DNA, diets were determined from prey remnants found within scats, and frequency of prey in scats was compared to expected values based on prey density estimates to test the hypothesis that diets of jaguar and puma were selective. Densities of major prey species were estimated using line-transect sampling. White-lipped peccary Tayassu pecari, collared peccary Tayassu tajacu and brocket deer Mazama sp. were less abundant, and coatis Nasua nasua more abundant, in the hunted area than in the non-hunted area. Jaguar and puma in both hunted and non-hunted sites obtained similar dietary contributions from large prey to their respective diets despite differences in the abundance of these prey species. Diets of jaguar and puma, as measured by percentage biomass occurrence of prey species, did not differ between hunted and non-hunted areas. Jaguar diets were dominated by medium-sized prey, particularly armadillos Dasypus novemcinctus and coatis, in both hunted and non-hunted areas. Medium-sized mammals also were prominent in puma diets, but large mammals constituted approximately 50% of prey biomass in both hunted and non-hunted areas. Deer Odocoileus virginianus and Mazama sp. and large rodents Agouti paca and Dasyprocta punctata were the most important prey of puma. Dietary overlap between jaguar and puma in both hunted and non-hunted areas was low.

Patterns of association in many ungulate species vary throughout the year, with males periodically segregating from females. Sexual segregation can occur if males and females use different habitats (habitat segregation), occupy exclusive ranges (spatial segregation) or occur in separate social groups (social segregation). Previous studies on social segregation in ungulates have focused mostly on non-reproductive periods and species in temperate systems with short mating seasons. This study examined social segregation in African buffalo Syncerus caffer at Hluhluwe-iMfolozi Park, South Africa, during their 6-month mating season. During this period, mature male buffalo alternated between joining mixed-sex herds which comprise females and young, and small all-male groups. Activity patterns of male buffalo in both group types were examined to determine if differences in time allocation or activity asynchrony could explain the observed segregation. Mature males foraged for less time than both adult females and younger males when they were with mixed herds. Mature male buffalo differed in how their active time was apportioned to foraging and reproductive activities between the two group types. Females maintained group cohesion despite only low synchrony in activity, therefore segregation of male buffalo could not be explained by the activity budget hypothesis. For males in mixed-sex herds, reproductive activities were apparently at the expense of foraging time. The high time and energy costs of reproductive activities were probably responsible for the periodic separation of male buffalo from mixed herds during the extended mating period.

Caecilians are an order of amphibians with distribution confined to several of the tropical countries. They are subterranean animals and practice a form of internal fertilization. Several species are viviparous. Published reports on seasonal variation in male reproduction in caecilians are limited to a very few species. A study was undertaken to examine the seasonal variation of testicular activity with respect to spermatogenesis and steroidogenesis in a caecilian, Ichthyophis tricolor, fairly abundant in the Western Ghats of Kerala, India, using light and transmission electron microscopy, terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) staining and biochemical determination of 3-hydroxy-Δ5-steroid dehydrogenase (Δ5-3β-HSDH) activity. Three phases in spermatogenic activity, active spermatogenesis (July–November), early regression (December–March) and spermatogenic quiescence (April–June) are identified. Apoptosis seems to be the mechanism of germ cell death during the regression phase. Leydig cells are interstitial and not peritubular. Activity of testicular Δ5-3β-HSDH follows the same pattern as spermatogenic activity, although histometric data on the interstitial tissue reveal higher areas during the regression and quiescent phases. Our findings will be useful in evolving strategies for conservation of caecilians with special reference to Kerala, India.

Dispersal influences the dynamics and persistence of populations, the distribution and abundance of species, and gives the communities and ecosystems their characteristic texture in space and time. The Eurasian lynx Lynx lynx is a medium-sized solitary carnivore that has been re-introduced in central Europe and currently occurs in rather small populations, where dispersal is believed to play a prominent role for the recolonization of unsettled areas and persistence of subpopulations. Between 1988 and 2001 the spatio-temporal behaviour of sub-adult Eurasian lynx was studied in two re-introduced populations in Switzerland, based on 31 juveniles of which 24 were radio-tagged to find out which factors influence dispersal. Age at independence ranged from 8.1 to 10.7 months and did not differ between populations or sex. Independence began from January to the beginning of May with a peak in April. After independence, sub-adults stayed a few days in the maternal home range. Age at dispersal differed between the areas of origin and was possibly affected by sex and the presence of new progeny. Dispersers of both sexes established transient home ranges; however, only one male in the saturated population established a transient home range. Although only females took over the maternal home range, there was no significant sex bias in the proportion of individuals that dispersed in both populations. Successful dispersers settled in a territory at distances that differed between populations with effects of sex, but not condition. The mean dispersal distance in the high-density population was 25.9 km compared to 63.1 km in the low-density population. Dispersal distances in the high-density population – shorter than those reported in other Eurasian lynx studies but comparable to those observed in an Iberian lynx population – are limited by habitat restrictions hindering connections with a neighbouring population.

Ambush and active foraging are held to be discrete foraging modes having important theoretical consequences and evolutionary correlates, but foraging variables (number of movements per minute (MPM) and per cent time spent moving (PTM)) vary continuously. Whether foraging movements are unimodally or bimodally distributed is controversial. Foraging modes have been crucial for understanding taxonomic, morphological, ecological, and behavioural diversification of lizards. Extensive data for them are used to examine the modality-continuity controversy. MPM and PTM are lognormally distributed, confirming continuity and unimodality. By separating species into groups of ambush and active foragers, bivariate cluster analysis supports the view that lizards fall into active and ambush modes that may reflect adaptive peaks of joint MPM and PTM values. Phylogenetic analysis is needed to test relationships between variables. Although it has greatly advanced understanding of relationships between foraging and other variables, a two-mode paradigm is too simplistic. Modes defined solely by MPM and PTM may obscure differences in speed and search methods. Overlap between clusters might occur in nearly unstudied major taxa that forage differently. On the MPM×PTM plane connections among ambush, active, and saltatory (start-stop) foraging are apparent, suggesting that saltatory foragers may occur in lizards. Controversies about continuity, bimodality, and dichotomy of modes are resolved. Clusters represent common combinations of unimodally distributed MPM and PTM occupying limited regions of foraging space. Some species fall outside traditional modes, but examination of correlations between clusters and other variables remains a viable approach.

Osteophagia, variable serum calcium (Ca) and phosphorus (P) concentration, high serum alkaline phosphatase activity, a high growth rate, and a large skeletal mass, all suggest that Ca and P requirements and availability are finely balanced in giraffes. The mineral content of some marker bones in skeletons obtained from adult male giraffes (browsers) and adult male African buffaloes (grazers of similar body mass) were compared to assess the idea of critical Ca and P balance. Our results show that the P concentration of plasma varies more than Ca concentration, and that the Ca content of giraffe bones (0.196±0.01 g/g) and buffalo (0.202±0.006 g/g) varies more than P content (0.095±0.002 in both). The average Ca and P content of the bones analysed was similar in both species (Ca=∼20.0%, P=∼9.5%). Giraffe skeletons, however, contain three times more Ca and P than do buffalo skeletons. This translates into a 1.5–2.0 fold higher Ca requirement for giraffes, with which they seem to cope effectively by selection for Ca-rich, dicotyledonous, browse. Sources of P to meet requirements are not obvious and a seasonal deficiency of P is a more likely cause of observed osteophagia than Ca deficiency. Giraffe rib P density, the best measure of P balance, of 0.142±0.01 g/cm3 is, however, above the deficiency threshold. Bone mineral content (Ca and P) correlates well with bone density and shows only slight differences between adult males of the two species.

The timing of reproductive events is critical for fitness, and these events are often linked to weather and climate. Weather components are thought to influence the nesting behaviour of freshwater turtles, but to date there have been few quantitative studies and no comparative studies. We compared the environmental cues used by nesting Australian (Emydura macquarii and Chelodina expansa) and North American (Chrysemys picta) freshwater turtles, and quantified the differences in weather between days with and without nesting activity within the nesting season. We also characterized the diel time of nesting for each species. The results suggest that nesting behaviour is related to warm air and water temperatures in C. picta and to rainfall in E. macquarii and C. expansa. Chrysemys picta primarily nests in the afternoon and evening, E. macquarii is a crepuscular nester, and C. expansa nests diurnally. While changes in life history resulting from climate change are difficult to predict, we suggest that an increase in the number of El Niño events may have adverse effects on the two Australian species, whereas increases in environmental temperature may expand the number of nesting opportunities for C. picta.

Data on 22 radio-collared adult female roe deer Capreolus capreolus in the Chizé forest were used to test whether their home-range size was influenced by resource availability and reproductive status. As roe deer females are income breeders and invest heavily in each reproductive attempt, they should be limited by energetic constraints. Thus it was expected that: (1) heavier females should have larger home ranges; (2) that home-range size should decrease with increasing vegetation biomass; (3) home-range size should increase with increasing reproductive effort (i.e. females with two fawns at heel should have larger home ranges than those with one fawn, which should have larger home range than females without fawns). To test these predictions, variation in spring–summer home-range size was studied in 2001 and 2002, using 95% kernel home-range estimation. Results showed that females do not adjust their home-range size in response to body mass or age. Home-range size increased with increasing reproductive success, but the magnitude of the change varied over the period of maternal care. Finally, although their home-range size decreased with increasing plant biomass (slope = −0.11, SE=0.065), female roe deer at Chizé did not fully compensate for declines in food availability by increasing home-range size.

Lions Panthera leo are generally thought to prey on medium to large ungulates. Knowledge of which species are actually preferred and which are avoided is lacking, however, as is an understanding of why such preference or avoidance may arise. An analysis of 32 studies over 48 different spatial locations or temporal periods throughout the distribution of the lion shows that it preferentially preys upon species within a weight range of 190–550 kg. The most preferred weight of lion prey is 350 kg. The mean mass of significantly preferred prey species is 290 kg and of all preferred species is 201 kg. Gemsbok, buffalo, wildebeest, giraffe and zebra are significantly preferred. Species outside the preferred weight range are generally avoided. Species within the preferred weight range that are not significantly preferred (such as roan, sable and eland) generally have features that reduce predation either morphologically (e.g. sable horns), ecologically (e.g. roan and sable occurring at low density), or behaviourally (e.g. the large herd size and increased vigilance of eland). Warthog are below the preferred weight range yet are taken in accordance with their availability and this is probably due to their sympatry with lion, their relatively slow evasion speed and their lower level of vigilance. Plots of prey preference against prey body mass follows a bell curve with a right skew that, we argue, is caused by collective hunting by lions of larger-bodied prey. Our methods can be used on all large predators and are likely to be useful in assessing competition in sympatric communities of predators, cooperative hunting and predicting predator diets. This will allow us to move beyond descriptive dietary studies to improve our predictive understanding of the mechanisms underlying predator–prey interactions.

Numbers of great cormorants Phalacrocorax carbo feeding in inland waters during winter have increased throughout Europe resulting in concerns over their impacts on fisheries. Loch Leven is a world-renowned sport fishery for trout and supports a nationally important population of wintering cormorants. The relationships between brown trout stocking, regional cormorant numbers and cormorants counted during winter on Loch Leven were examined. Stocked brown trout were fin-clipped before release and gut contents from a sample of 96 cormorants shot under scientific licence were analysed. The data suggest that the number of cormorants at this site is influenced by both the stocking policy and the regional population level. Cormorant diet varied with the sex and age of birds. Overall, trout made up c. 85% of the total content by weight. Brown trout predominated in the diet, making up c. 70%, while rainbow trout occurred less frequently, making up c. 6%. Trout which could not be identified to species, made up the remainder (c. 9%). There was no significant difference in the ratios of wild and stocked brown trout sampled from the loch and from cormorant stomachs in winter. A model was constructed to investigate the likely loss of trout to cormorants roosting on the loch. It was estimated that over a 7-month period cormorants consumed 80 803 (41 617–128 248) brown and 5213 (830–12 454) rainbow trout. These estimates compared to average annual fishery catches of 5828 brown and 12 815 rainbow trout (1996–2000). Comparison with published estimates of trout populations in Loch Leven indicated a high potential for competition between the birds and the fisheries for available fish. It is suggested that stocking has led to an increase in cormorant numbers and the subsequent increase in predation may have prevented any increase in the trout population or in fishery catches.

This work presents new data from 48 maned sloths Bradypus torquatus captured between November 2002 and November 2003 in three regions of the Atlantic forest where the largest remnant populations of this species are found. Data from another long-term study, carried out from 1994 to 1996 and from 1999 to the present (n=14), were also used, making a total sample of 62 sloths. Average adult body weight is 6594±236 g and average head-body length is 66.5±0.8 cm (n=35), indicating that Bradypus torquatus is the heaviest of all four Bradypus species. Individuals from lower-montane forests (600–1000 m a.s.l.) are significantly larger (head–body length; t-test; P=0.001) than individuals from the lowlands (<350 m a.s.l.), suggesting altitudinal differentiation between populations. Sexual dimorphism, here reported for the first time, was found in body length (females are significantly larger than males) and in other external characters, such as mane size and form (darker and larger in males), and size and shape of the external genitalia. Most differences between sexes are, however, only discernible in reproductively active individuals. Breeding is slightly seasonal; minimum observed interbirth interval was 1 year and litter size was always one. Infants stayed with their mothers until 8–11 months old; started feeding on solid food as early as 2 weeks old but continued suckling until c. 4 months of age. Age of sexual maturity was estimated at 2–3 years and the oldest captured maned sloth was a healthy male who was at least 12 years of age. Overall, results indicated that maned sloths are similar in these aspects to congeneric species. Information presented here significantly improves the current knowledge on this endangered sloth species and is useful for the proper planning and implementation of in situ conservation strategies such as translocations and reintroductions.

Comparative analysis of the biology of insular and mainland populations has demonstrated a number of differences in characteristics of insular populations, termed the ‘island syndrome’. A subspecies of Arctic fox on the Commander Islands (Alopex lagopus semenovi on Mednyi Island) has been isolated for an evolutionarily significant time in small territories at the periphery of the species' range. The number of foxes on Mednyi had been observed to be very high since the islands were discovered in 1741, but a drastic decline in population density in the late 1970s, owing to mange, has left the population low. The aim of the study was to determine whether the Mednyi Arctic fox population exhibited the features expected in an isolated insular population, such as difference in body size, increased population density, larger social groups, lower tendency to disperse and lower fertility, and whether any behavioural changes were evolutionarily reinforced or were a temporal response to current ecological factors on the island. Eight predictions were identified based on the island syndrome, of which the Mednyi Arctic foxes conformed to seven. We suggest a new prediction, namely that the tendency for increased sex dimorphism in dispersal may also be a distinguishing feature of insular populations. All the features displayed by the insular population on Mednyi – conservative use of space, increased tendency to form complex groups, decreased fertility and dispersal – seemed to be preserved regardless of the currently comparatively low populations. Thus, although foxes have been below carrying capacity for at least 10 generations, island syndrome characteristics have persisted.

Animals inhabiting environments with low productivity and food availability commonly have reduced energy demands and increased digestive efficiencies. The dry matter intake (DMI), apparent digestible dry matter (ADDM), digestible efficiency (DE) and digestible energy intake (DEI) of two populations of common spiny mouse Acomys cahirinus were compared during both winter and summer under conditions of simulated water stress. Mice were captured from the north- and south-facing slopes (NFS and SFS) of the same canyon that represent mesic and xeric habitats, respectively. Measured variables were also compared between F1 mice that had been born to either NFS or SFS mice, and raised in the laboratory. SFS mice were able to assimilate energy more efficiently than NFS mice during the summer. By comparison, NFS mice were able to assimilate more energy during the winter. During winter, NFS mice assimilated more energy at low levels of water stress, whereas SFS mice assimilated more energy at higher levels. Differences were also apparent in F1 mice. It is therefore suggested that local climatic conditions can impose physiological adaptations that are retained in succeeding generations, creating unique meta-populations.

With an increase in the popularity of wildlife ranching in southern Africa has come the introduction of non-native (extralimital) mammalian herbivores. Financial gain has arguably been at the forefront of these introductions, with little or no assessment of the ecological consequences. The diet of three populations of introduced giraffe Giraffa camelopardalis was assessed by direct observation in the Eastern Cape Province, South Africa between January 2002 and October 2003, as the first step towards understanding the ecological role played by giraffe in the region. Similar to the diet of giraffe within their native range, a deciduous species from the genus Acacia (Acacia karroo) was the most important species in the diet. Giraffe in the Eastern Cape Province, however, consumed more evergreen species than those within their native range. The relative lack of deciduous species in the Eastern Cape Province provides a probable explanation for such a result. Seasonal variation in the consumption of the most important species in the diet was evident with members of the genus Rhus being more important in the winter months. This was attributed to the deciduous nature of A. karroo. The potential for giraffe to have a detrimental effect on the indigenous vegetation is discussed. We conclude that the study provides a much-needed list of plant species threatened by giraffe browsing in a region where the vegetation is thought to have evolved in the absence of such a browser.

The Cape mole-rat Georychus capensis is a solitary subterranean rodent that exhibits seasonal reproduction. This study set out to determine whether the female Cape mole-rat is an induced or spontaneous ovulator. Eleven females were collected from the field just before the breeding season and housed individually. Urine was collected for 5 weeks. Females were subjected to one of three trials: housed separately without a male; allowed only non-physical contact with unvasectomized males; placed in direct contact with four vasectomized males. Urine was collected for a further 5 weeks and urinary progesterone profiles established. Females housed in direct contact with males exhibited heightened progesterone concentrations and the presence of corpora lutea in their ovaries. The act of coitus seems to be necessary for ovulation to occur in the females even though males were not capable of fertilization.

We examined whether synchrony and timing of breeding influenced magnitude and timing of sexual segregation in sympatric western grey kangaroos Macropus fuliginosus and red kangaroos M. rufus, at Hattah-Kulkyne National Park, in south-eastern Australia. These species vary in the synchrony and timing of their mating activity: western grey kangaroos mate during a relatively synchronous period, predominantly during spring, while red kangaroos mate throughout the year. Surveys were conducted during autumn and spring 2000 to examine seasonal patterns of mating activity, group composition, spatial distribution, and habitat selection of adults of both species. Habitat selection was also examined by analysing data from culls conducted from 1998 to 2002. Mating activity occurred synchronously in western grey kangaroos, thus, like in many ungulate species, there was a time of peak segregation, during autumn, when females were in lactational anoestrus, and a time of peak aggregation, during the period of peak mating activity in spring. In red kangaroos, mating activity occurred during both seasons, but showed a slight peak during autumn. Consequently, segregation was weaker than in western grey kangaroos but occurred through-out the year, with a slight peak during spring. The degree of social and spatial segregation in western grey and red kangaroos was comparable to that in ungulates, while habitat segregation was considerably lower than is typically seen in ungulates. These results indicate that breeding phenology is a major factor involved in sexual segregation, and highlight the importance of directing attention at the general conditions underlying this phenomenon.

A diverse small mammal fauna inhabits the tropical savannas of Kakadu National Park in northern Australia. A detailed long-term capture–mark–recapture study was conducted to estimate body growth parameters in relation to intrinsic and extrinsic factors that may influence them. Three non-linear growth increment functions were compared to determine which one best represented the general growth patterns of nine small mammal species at Kapalga. The von Bertalanffy growth increment function provided the best fit to a pooled species dataset. Hierarchical mixed-effects models were then used to examine variation in body size asymptote and growth and account for non-independence of observations. Model selection was based on the Kullback–Leibler information theoretic approach. As expected, the body size growth constant was correlated to body mass at Kapalga, and body size sexual dimorphism was evident in most species. Difference in body growth constant was only evident in Isoodon macrourus, where females showed accelerated growth. Three of the four marsupial species exhibited either temporal (annual) and spatial (catchment level) variation in body size asymptote, whereas rodent species showed none. There was no clear influence of other extrinsic factors such as fire treatment, rainfall or habitat on body size asymptote or growth rate constant. Our results suggest that body growth is largely controlled by intrinsic factors for each species such as gender in small mammal species at Kapalga. Change in body size and growth caused by human-induced changes to the landscape from factors such as altered fire regimes is unlikely to be substantial for tropical small mammals in northern Australia.

This study focuses on possible sources of egg size variation in the northern lapwing Vanellus vanellus, a polygynous shorebird with more variable male than female reproductive success. From the hypothesis that female birds allocate more resources into male than female eggs to improve their sons' abilities to compete for mates, male eggs were predicted to be larger than female eggs, and the proportion of sons was predicted to increase with mean egg volume of clutches. However, no size differences between male and female eggs were found. Corresponding with earlier reports in the species, egg size was positively correlated with female body condition, but no relationship between offspring sex ratios and intra-clutch mean egg volumes was detected. These results suggest that a higher variation in reproductive success among males than among females is not sufficient for sexually dimorphic eggs to evolve in birds. Moreover, previous studies have suggested that shorebird eggs are subject to stabilizing selection for equal size within clutches. In contrast, this study demonstrates a consistent variation in egg size, with a significant increase in egg breadth between first and second eggs, and decreases in both breadth and volume between the third and the final fourth egg. The volume of last-laid eggs was on average 2.3% smaller than the mean size of the preceding three eggs. Among the shorebirds studied so far, this consistent pattern of intra-clutch egg size variation is unique to lapwings.

During the last two decades, populations of the wild boar Sus scrofa in Europe have increased considerably and the species has spread into new areas over the entire continent. Because of the animals' impact on agriculture, livestock and biodiversity, and the resulting necessity of realistic management practices, we were interested in the key environmental factors responsible for this remarkable development. The study was based on data from the canton Thurgau, a region in north-eastern Switzerland. We used data on damage and hunting success to calculate a population density index and related it to eight variables describing ecological conditions, demography and hunting pressure (measured by the number of hunters) over a 25-year period. The analysis shows that the population increase correlates with higher than average winter and spring temperatures and improved food supply through more mast years and an increase in the area of maize cultivation. While favourable temperature conditions mainly reduce juvenile mortality, enhanced food availability is likely to boost reproductive success through younger age at first reproduction, larger litter size and earlier onset of oestrus within a season. Given this link between food and reproduction, supplemental feeding, a management practice recommended and very common all over Europe, should be reconsidered.

In constructing large vegetated mounds, Macrotermes termites play a key functional role in many African savanna systems. This study focuses on ungulate feeding on Macrotermes termitaria vegetation in Lake Mburo National Park, Uganda. With the exception of oribi Ourebia ourebi, all the species studied (i.e. impala Aepyceros melampus, Burchell's zebra Equus burchelli, Defassa waterbuck Kobus ellipsiprymnus, topi Damaliscus lunatus, bushbuck Tragelaphus scriptus and warthog Phacochoerus africanus) grazed preferentially on mound areas compared to the adjacent savanna. Ruminant species grazed closer to termitaria than non-ruminants and female impala both browsed and grazed closer to mounds than males. No sexual difference in grazing distance to mounds was found for waterbuck.