Over one million pairs of seabirds breed annually on the Houtman Abrolhos island group, off the mid-western coast of Australia, the largest seabird breeding station in the eastern Indian Ocean. Eight of the 13 species that breed annually on Pelsaert Island are terns. Dietary samples (regurgitates) were collected from the five most numerous tern species from 1993 to 1999. The prey items identified were related to observations of foraging seabirds around the island. The largest species studied, the crested tern Sterna bergii, foraged mainly for reef fish over shallow reef flats near the breeding islands, as well as for schooling clupeid fish over coastal shelf waters. The smallest species, the roseate tern S. dougallii, also foraged within sight of its colonies, but over deeper waters than crested terns. Three larval fish species characteristic of continental shelf waters (a gonorhynchid, a goatfish and a bellowfish) figured prominently in the diets of roseate terns and three other tern species studied. Of these, only the sooty tern S. fuscata also ate squid and lanternfishes, foraging farthest (480–600 km) from its breeding island, off the shelf edge. The lesser noddy Anous tenuirostris and brown noddy A. stolidus took very similar taxa of prey and also overlapped considerably in their foraging ranges, about 180 km from their colonies, between the islands and the continental shelf edge. However, the lesser noddy took smaller fish than did the larger brown noddy. Although these five abundant tropical tern species, that bred sympatrically, showed some segregation in their diets and, more clearly, in their foraging ranges, considerable overlap of both aspects remained.

Results from a large-scale, capture—recapture study of humpback whales Megaptera novaeangliae in the North Atlantic show that migration timing is influenced by feeding ground origin. No significant differences were observed in the number of individuals from any feeding area that were re-sighted in the common breeding area in the West Indies. However, there was a relationship between the proportion (logit transformed) of West Indies sightings and longitude (r2=0.97, F1,3=98.27, P=0.0022) suggesting that individuals feeding farther to the east are less likely to winter in the West Indies. A relationship was also detected between sighting date in the West Indies and feeding area. Mean sighting dates in the West Indies for individuals identified in the Gulf of Maine and eastern Canada were significantly earlier than those for animals identified in Greenland, Iceland and Norway (9.97 days, t179=3.53, P=0.00054). There was also evidence for sexual segregation in migration; males were seen earlier on the breeding ground than were females (6.63 days, t105=1.98, P=0.050). This pattern was consistently observed for animals from all feeding areas; a combined model showed a significant effect for both sex (F1=5.942, P=0.017) and feeding area (F3=4.756, P=0.0038). The temporal difference in occupancy of the West Indies between individuals from different feeding areas, coupled with sexual differences in migratory patterns, presents the possibility that there are reduced mating opportunities between individuals from different high latitude areas.

The relationship between the population dynamics of ricefield rats Rattus argentiventer and their food supply, rice plants, was investigated in an enclosure in Jatisari, West Java. The density of the rat population fluctuated greatly throughout the year depending on the growth stages of the rice plants. A model illustrating the responses of the rat population to the growth stages of the rice plants is described. The population increased following periods when high-quality rice plants were available, and decreased following periods when only low-quality rice plants were available. The highest rate of increase (r) over a 2-week period was observed during the dry season of 1989 (r=1.77). The lowest rate of increase over 2 weeks was observed during the rainy season of 1989–90 (r=−0.59). The maximum rate of increase for the ricefield rat in the numerical response function was 1.183 month−1, and the best estimate for the numerical response function was robs=−3.890+5.043(1−e−0.026V).

The external orofacial morphology, perioral bristle distribution and feeding behaviour of Dugong dugon, Trichechus inunguis, T. senegalensis and T. manatus are described. Despite their differing orofacial morphology, dugongs and trichechids possess six similar regions: the oral disk, orofacial ridge, supradisk, chin and upper and lower bristle (modified vibrissae) pads. All living sirenians possess six discrete fields of bristles: four on the upper lip (U1, U2, U3, and U4) and two on the lower lip (L1 and L2). The distribution of these fields is similar among all living sirenians with the exception of the U1 bristle fields in dugongs. Perioral bristle field boundaries are distinguished by distinct changes in their length-to-diameter ratios. Both dugongs and trichechids possess bristle-like hairs covering the oral disk, which possess length-to-diameter ratios intermediate between perioral bristles and postcranial hairs. Sirenians use elaborated facial musculature in conjunction with perioral bristles to acquire, manipulate and ingest aquatic vegetation. The U2 and L1 fields are the primary bristles used to ingest vegetation. The use of the L1 bristle fields is similar among all living sirenians. However, dugongs and trichechids are divergent in their use of the U1 and U2 bristle fields. Dugongs use the U2 bristles fields in a medial-to-lateral motion, while all trichechids use the U2 bristles in a prehensile, lateral-to-medial, grasping motion. These divergent behaviours presumably allow dugongs to exploit benthic foraging (i.e. consumption of rhizomes) to a greater degree than trichechids. Functional hypotheses of rhizome excavation are presented for both dugongs and trichechids.

Amphibious animals may be subject to strong but conflicting selective pressures to enhance locomotor performance both on land and in the water. Biomechanical models suggest that in snakes, adaptations to swimming (e.g. reduction of ventral plates, flattening of tail) will reduce their ability to move on land. The locomotor speeds of six taxa of amphibious (laticaudid) sea-snakes, plus one entirely marine (hydrophiid) species were measured. Because the relative dependence on aquatic vs terrestrial habitats varies with a laticaudid's species, sex and body size, a previous study predicted that these factors should generate significant variation in locomotor speeds within laticaudids. Measurements of swimming and crawling speeds supported this prediction. Some species were faster than others and, within each species, males were faster than conspecific females. The degree of locomotor superiority of males was greater for terrestrial (>40%) than for aquatic (20%) locomotion. Smaller snakes were faster than larger animals in relative speed (body lengths/s) but slower in absolute terms (m/s). The hydrophiid Emydocephalus annulatus was slow in water as well as on land, perhaps because it eats immobile prey and thus, does not depend on speed for foraging. The diversity of locomotor abilities within laticaudid sea-snakes provides a remarkable opportunity to identify factors that influence evolutionary trade-offs between conflicting evolutionary optima.

Jaguar Panthera onca and puma Puma concolor are sympatric throughout the jaguar's distribution. Although several studies have focused on the interactions between these two predators, the ecological and behavioural factors that promote their coexistence remain unclear. The goal of this study was to identify those factors that facilitate the coexistence of these cats in a mosaic landscape in the Venezuelan llanos. The study was conducted from January 1996 until November 1998. Five jaguars and six pumas were captured and radio-collared. A high degree of spatial overlap was observed between jaguars and pumas, which may be related to the abundance and distribution of prey species. At a fine scale, there was little overlap of puma locations with jaguar locations. Both species were more active at night than during daytime, but seasonal differences were detected in the activity levels of these predators. Major segregation was found in food habits. Jaguars selected for large prey and pumas for medium-sized prey. Jaguars selected for capybara Hydrochaeris hydrochaeris and collared peccary Tayassu tajacu and consumed caiman Caiman crocodilus and white-tailed deer Odocoileus virginianus less than expected. Pumas selected just for collared peccary and also killed caiman less than expected. It is suggested that the abundance of medium-sized prey is an ecological factor that is facilitating the coexistence of jaguar and puma in the study area. Habitat heterogeneity may be another influential factor leading to the coexistence. Seasonal differences in activity levels probably reflect differences in the size and species of prey taken by these cats.

Pikas (Ochotona spp.) are burrowing herbivorous mammals believed to play a keystone role in determining the biodiversity of steppe ecosystems. Impacts of domestic livestock grazing on the distribution and abundance of the Daurian pika Ochotona daurica were investigated in eastern Mongolia where the species is widespread and abundant. Effects of pikas on plant species richness and vegetation coverage were examined at different distances from burrow systems. Daurian pikas were nearly absent from severely grazed study sites, and incidence of the species increased with decreasing grazing intensity. The number of occupied burrow systems and usage of burrows was higher in sites with lower grazing pressure. Plant species richness and ground cover was higher at 3–12 m from the burrow systems than directly over burrows, suggesting that the effect of Daurian pikas is limited to the burrow system. Contradictory to previous studies on grassland pikas, this study indicates that Daurian pikas suffer from overgrazing and that their impact on grassland is only light.

The seasonal activity of Leisler's bat Nyctalus leisleri and pipistrelle bats Pipistrellus spp. with respect to minimum bat numbers and habitat use were investigated in County Down, Northern Ireland using a driven transect from April 1998 to October 1998. Data were collected in lowland farmland near Belfast, Northern Ireland using two BatBox III bat detectors tuned to detect both species and species groups simultaneously. The number of bats/km increased during April, May and June, peaking in July and tailed off after this period. The main peak in July is assumed to reflect the occurrence of newly volant young. An increase in the number of pipistrelle social calls during August and September probably represented mating activity. Bat activity correlated with temperature in both N. leisleri and Pipistrellus spp., although bat numbers were independent of temperature after the middle of June. There was significant variation in habitat use by pipistrelle bats along roads over the study period. Pipistrelle bats were observed in greater numbers in areas of tree-line, cut hedge (≤1 m high) and deciduous woodland, and increased further when these habitats bordered both sides of the road. Nyctalus leisleri was found in similar numbers in all habitat types and there was no seasonal variation in habitat use. The validity of this method for revealing seasonal variation in bat numbers and habitat use is discussed. Ambient climatic conditions may affect the number of bats recorded, while some species with long-range echolocation calls, such as N. leisleri, may defy analysis of habitat associations.

Changes in the spatial pattern of flocks of barnacle geese Branta leucopsis were examined in relation to individual behaviour during feeding visits to farm pastures. The flocks were photographed every 10–20 min, and the shape and location of the flock was determined from a plan view obtained from digitized images of the photographs. Flocks initially maintained a tight formation shortly after arrival, but then tended to expand with increasing residence time. The rate of expansion, however, was significantly greater in large flocks, with small flocks showing no consistent pattern. Observed rates of change in flock area were compared with those obtained from a simple model of flock movement in which individuals followed a random walk and moved at a constant speed. In contrast to the observed data, small simulated flocks (with relatively more edge birds) showed the greatest relative increase in flock area. This discrepancy between the data and the simulation can be explained mechanistically by differences in the behaviour of individuals in flocks of different sizes. In large flocks, birds at the leading edge of the flock had faster step rates and travelled further than birds in the centre and at the trailing edge. Rates of movement in small flocks did not vary with flock position. Levels of vigilance were higher during the first 10 min after arrival, in males, in smaller flocks and at the edges of flocks. Thus, upon arrival, flocks maintain a tight defensive formation with high vigilance, but with increasing residence time, vigilance decreases and larger flocks expand, suggesting a need for individuals to reduce feeding competition.

The prey brought in by 80 cats Felis catus over 1 year was monitored in two suburbs of Auckland, New Zealand: one suburb was completely urban, the other on the urban/forest fringe. Cat owners were asked to record and, if possible, keep the prey that their cats brought in. Rodents were the main prey brought in by domestic cats in the urban/forest fringe habitat, whereas invertebrates were the main prey in the fully urban habitat. Birds were caught in similar numbers by cats in both areas and were the second most important prey group at both study sites. However, more native birds were caught by cats in the urban/forest fringe area than in the fully urban habitat. Lizards were caught in similar numbers and were the third most important prey group in both study areas.

The effects of UV-A and UV-B (Cracow District, Poland, 50°04′N, 19°57′E; 220 m a.s.l.) on oxygen consumption were studied in common toad Bufo bufo (L.) tadpoles (Gosner stage 27). Ecologically relevant chronic doses of UV were simulated in the laboratory. Larvae separated for experiment were derived from UV-exposed or not exposed embryos. After hatching, tadpoles in stages 24–27 were treated with UV-A or UV-B. UV-A caused significant increases in oxygen consumption in larvae grown from untreated embryos, whereas no changes occurred in tadpoles irradiated with UV-A during embryonic and larval development. UV-B caused significant decreases in oxygen consumption in all exposed tadpoles. The changes were larger in larvae derived from eggs not exposed to UV-B than in tadpoles grown from UV-B-treated embryos. Our results suggest that ambient levels of UV-A and especially UV-B may affect the metabolic rate of common toad larvae living in shallow habitats. Affected respiration may retard development as well as increase the susceptibility of tadpoles to ecologically relevant pathogens. On the other hand, it seems that UV-irradiation induces some adaptive processes during embryonic development, which increase the resistance of the larval respiratory system to solar UV radiation.