This study examines aspects of the nesting behaviour of Brants' whistling rat Parotomys brantsii, a medium-sized rodent indigenous to southern Africa. In the semi-arid regions in which it occurs P. brantsii breeds opportunistically, modifying its breeding period in relation to rainfall. Within a winter rainfall area, females produced up to four litters of three to four young during the winter–spring period following a gestation period of c. 38 days, with females showing a post-partum oestrus. The behaviour of females was modified by the birth of their pups, after which they spent extended periods underground, interspersed with bouts of food-collecting activity. With the emergence of pups above-ground, females increased their vigilant activity. At 5 weeks pups had developed all the important behavioural characteristics of adults, such as creating their own overnight food stores, collecting nesting material and defending a warren area against conspecifics. This was also the age at which the young dispersed from their natal nest area as well as the time at which females could reach sexual maturity, despite physical immaturity. The high reproductive output of female P. brantsii, as well as the rapid ontogeny of their young, compared to other otomyine rodent species, may represent an adaptation for maximizing reproductive potential in the semi-arid areas they inhabit.

Oreochromis alcalicus grahami is a small cichlid fish that lives in the hot, highly alkaline, highly saline peripheral lagoons of Lake Magadi, Kenya. The fish faces profound diurnal oscillations of oxygen concentration. During the day, from photosynthetic activity of cyanobacteria (blue-green algae), the water is supersaturated with oxygen but after sunset when photosynthetic activity stops the water is virtually anoxic as a result of bacterial respiration. During the night and after explosive exercise, O. a. grahami characteristically skims the surface of the water with the mouth agape, suggesting that the buccal cavity is used as a gas-exchange organ. Contrary to expectation, however, the buccal cavity was found to be conspicuously non-vascularized: the surface epithelial lining was fundamentally of a mucus secretory type. In addition, certain cells in the deeper layers showed extensive lateral labyrinths similar to the epithelium of the renal tubules. These morphological features respectively indicated roles of secreting a protective film and regulation of ions taken across the epithelial lining of the buccal cavity. The allocation of gas-exchange to the gills and the air-bladder, osmoregulation essentially to the gills, and mucus secretion/protection to the buccal cavity displays an adaptive trade-off process in an elite animal. Effective use of the buccal cavity as a gas-exchanger would entail air-gulping followed by brief retention of it in the cavity to allow oxygen uptake. During such interval, both the gills and the air-bladder would of necessity be rendered temporarily non-functional. Skimming the top layer of water with the mouth open ensures that the gills are passively ventilated with well aerated water and the air-bladder is simultaneously used for gas-exchange, a strategy that should enhance oxygen acquisition, especially at higher ambient temperatures.

The duration of activity bouts by pine martens Martes martes was studied in the pristine deciduous forests in Białowieża National Park (north-eastern Poland). From 1991 to 1996, 14 martens were monitored by radio-tracking throughout 5823 h. On average, male martens were active for 9 h/day and females for 8.5 h/day. The duration of the martens' diel activity varied greatly among bimonthly periods (from 2.8 h/day in February–March to 12 h/day in June–July). Martens decreased their activity from 13 h/day on warm days to 2.5 h/day on cooler days. In the winter months, when martens curtailed their activity, they often hunted larger prey or scavenged ungulate carcasses. On average, 69% of the martens' active time was during the night. The number of activity bouts per day varied from one to six (mean 2.6) and increased with growing ambient temperature. Activity bouts of males were significantly longer (4 h, on average) than those of females (3 h) and were not related to ambient temperature. The duration of short inactive bouts increased in the cold season and inactivity lasted longer in females than in males.

Parental recognition of offspring would be expected to evolve among densely populated species in which parental investment is large, and separations of the mother–pup pair are frequent. Although otariids present a well-developed system of mutual vocal recognition, evidence in phocids is weak. Furthermore, allo-suckling is prevalent in some species and may reflect confusion over the identity of pups. The vocalizations of grey seal Halichoerus grypus pups have been found to be stereotyped and individually distinctive on the Isle of May, Scotland. However, playback experiments showed that mothers fail to discriminate between the vocalizations of their pup and a non-filial pup. Moreover, widespread allo-suckling was observed. In contrast, grey seals on Sable Island, Nova Scotia, a population reproductively isolated from that of the Isle of May, show very little allo-suckling. This may reflect the presence of a recognition system that does not seem to be present on the Isle of May. During the 1999 breeding season on Sable Island, vocalizations of grey seal pups were recorded and playback experiments carried out to determine whether female grey seals respond differently to the playback of vocalizations of their own pup, a familiar pup and an unfamiliar pup. Grey seal mothers were found to make significantly more head turns and body movements towards the loudspeaker during the playback of their own pup call than during the playback of a familiar or unfamiliar pup call. In addition, there was no evidence of an effect of pup age. This suggests that female grey seals can discriminate between pup calls using the stereotyped and individually distinctive vocalizations of their pup, and that different selective pressures may be in operation between the Sable Island and Isle of May colonies.

Two Iberian wolf Canis lupus signatus packs were studied in the north of Portugal during spring and summer 1996. The study areas are located in two mountainous areas close to the Spanish border. Both regions presented a very low density of wild ungulates and intensive livestock production. The food habits and the livestock depredation of the wolves were considered. The study material included 87 dropping samples, interviews with shepherds, carcass investigation and government reports of livestock depredation. Prey preference was measured in both areas. Wolves fed exclusively on livestock, especially goats. Wolf attacks on goats affected mostly large flocks of > 100 heads, but where there were horses, wolves preyed preferentially on horses. In both study areas, sheep was recorded as a regular prey by the government reports but never appeared in the scat analysis results. This apparent contradiction will be discussed. The wolf's dependence on livestock can be explained by the scarcity of wild prey and the high density of livestock. Conservation of wolves in such impoverished areas depends on an efficient livestock depredation management plan and the reintroduction of native prey species.

The dive duration of 16 underyearling (6–12 months old) southern elephant seals Mirounga leonina during their second trip to sea was investigated using geolocating time–depth recorders. Underyearling seals had a lesser diving ability, with respect to duration and depth, than adult southern elephant seals. Individual underyearlings dived for average durations of up to 20.3 min and depths up to 416 m compared to durations and depths of 36.9 min and 589 m, respectively for adults. Dive duration was positively related to their body mass at departure, indicating that smaller seals were limited to shorter dive durations, perhaps as a result of their lesser aerobic capacity. All seals often exceeded their theoretical aerobic dive limit (average of 22.1 ± 18.1%). The number of dives exceeding the theoretical aerobic dive limit was not related to mass, suggesting that factors other than mass, such as foraging location or prey availability, may have been responsible for differences in diving effort. Foraging ability, indicated by the ability of the seals to follow vertically moving prey, was positively related to seal mass, indicating that small mass restricted foraging ability. The shorter dive durations of the smaller seals inferred that they had shallower dive depths in which to search for prey, thus restricting foraging ability. Although foraging ability was restricted by size, foraging success was found to be inversely related to mass, the smaller seals gaining a higher proportion of blubber than larger seals during their foraging trips. Thus, despite smaller seals being restricted to shallower depths and shorter durations, their foraging success was not affected.

Mortality is the most extreme effect of ultraviolet-B radiation (UV-B; 280–315 nm) on living organisms, but sublethal effects of UV-B may also be important. Moreover, there may be population differences in response to UV-B, but this aspect has not been well explored for animal populations. Amphibians have been a model system for studying the detrimental effects of UV-B. However, previous research on the effects of UV-B on amphibians has mainly focused on embryos. Few studies have investigated how UV-B affects larvae. We examined potential sublethal effects of UV-B on the long-toed salamander Ambystoma macrodactylum from two different populations. Observational data from field transects indicated that larvae are potentially exposed to UV-B in their natural habitat. Choice tests indicated that larvae select shaded regions more often than those in the sun, but do not directly distinguish between regions with high and low UV-B. Laboratory experiments indicated a survivorship difference between individuals from low- and high-elevation sites. When exposed to relatively low levels of UV-B individuals from low-elevation sites experienced higher mortality than controls (no UV-B). There were no differences in mortality between UV-exposed and non-exposed larvae from the high-elevation population. Although mortality of UV-B exposed larvae was not significantly different from controls in the high-elevation population, sublethal effects on growth were observed. Individuals from the high-elevation site grew significantly less when exposed to UV-B than individuals shielded from UV-B. Our study demonstrates that larval A. macrodactylum are exposed to UV-B in nature, that UV-B exposure can cause mortality as well as having sublethal effects on growth and that there are potential population differences in sensitivity to UV-B radiation.

The spatial and temporal compositions of rodent communities in habitats of the Badia region of north-east Jordan were investigated between 1996 and 1997. Live grid-trapping and spot-lighting techniques were employed to estimate rodent densities. Sixteen environmental variables including soil content, vegetation cover and relief were recorded within the study sites. TWINSPAN was used to derive six habitat classes based on the similarity of their rodent communities. These were hammada, harrat, marab, wadi and two types of sand dunes. The derived classifications were similar to the original categorization of habitat types based on ground-truthed observations of the sites selected from satellite imagery. Multivariate statistical analyses (TWINSPAN and DECORANA) revealed three major rodent groups in relation to local habitat types: (1) petrophiles: Gerbillus dasyurus, Acomys russatus and Meriones tristrami; (2) open hammada-dwelling species: Jaculus jaculus, Gerbillus henleyi and Meriones crassus; (3) psammophiles: Meriones libycus, Gerbillus nanus and Gerbillus cheesmani. Species richness was highest in marabs and lowest in red sand dunes. Species diversity (Hill's index) was highest in sand dunes and lowest in red sand dunes. Rodent biomass was highest in sand dunes and lowest in wadis. CANOCO showed rodent community composition to be correlated with vegetation parameters and soil content. TWINSPAN grouping and DECORANA ordination of rodent species provides some evidence for habitat preference, size disparity and competition as mechanisms of resource partitioning facilitating coexistence.

The density of nests of the magpie goose Anseranas semipalmata on the Mary River floodplain fluctuated markedly during 1988–93, failing almost completely in unfavourable (El Niño) years. Nest density and timing of nesting were strongly correlated with variations in the time of onset of the wet season, but were much less sensitive to rainfall quanta in the mid- to late wet season. Nest densities were higher and nesting was initiated earlier in breeding seasons preceded by sustained rainfalls during the transition from dry to wet seasons. Clutch sizes were slightly larger in years of early wet-season onset. Within seasons, later clutches contained fewer eggs and the eggs were smaller, probably as a consequence of later nesting by younger birds. Second clutches from a small sample of marked re-nesting birds and a pulse of nesting after flooding losses, contained similar numbers of eggs to first clutches, but the eggs were larger. Dependence of nesting on events occurring months before clutch initiation, when birds are using habitats distant from nesting colonies, illustrates the importance of integrated management of floodplain systems to meet year-round habitat needs, and the risks posed by homogenization of wetlands by improvement of pasture for grazing.

Pristina silvicola and P. terrena spp. nov. are described from soil samples of the primary rain forest at the Brazilian Agroforestry Research Facility near Manaus, Brazil. Living and preserved specimens were studied. The species are among the smallest oligochaetes known (1–1.5 mm long) but they are conspicuous by their brilliant, highly refractile coelomocytes. Pristina silvicola is also described from sexually mature specimens. Its character combination invalidates Pristinella as a genus separate from Pristina. Both genera are reunited as Pristina. Pristina silvicola and P. terrena, species which lack a proboscis, share a character combination that is unique in the genus: stomach absent, first nephridia in segment VII, ventral chaetae uniform with upper tooth not longer than lower. They differ from one another in the shape of the brain and in other details of the chaetae.

Maximum dive depths of common diving petrels Pelecanoides urinatrix were measured monthly over > 1 year, from January 1995 to February 1996, with miniature gauges attached to the birds at Mayes Island, Kerguelen Archipelago. Overall, maximum dive depths of 347 diving petrels averaged 31 ± 6 m (range: 8–64 m), with a mode at 30–35 m. Mean maximum dive depths differed significantly over the study period. The lowest value (22 ± 8 m) was obtained in winter and it was associated with euphausiid crustaceans, suggesting a change in foraging behaviour associated with a shift in the main prey consumed. During the breeding season, birds fed mainly upon the hyperiid amphipod Themisto gaudichaudii (66% of the total number of prey), followed by the large carnivorous copepod Paraeuchaeta antarctica (15%) and zoea larvae of the crab Halicarcinus planatus (13%). Comparison of the diving capabilities of diving petrels (genus Pelecanoides) with those of other diving seabirds suggests that, relative to body mass, diving petrels can dive deeper than penguins and also possibly than alcids, and are thus the most proficient divers among birds.

We studied home-range size, home-range overlap and use of habitat in a population of striped skunks Mephitis mephitis in eastern Tennessee. Variables determined to influence home-range size were season and body weight: skunks had larger ranges in the spring than in winter and heavier females had larger ranges. Habitat, sex and sample sizes of radio-fixes did not correlate with home-range size. All home ranges overlapped by 1.4–100% of the range area. There was no pattern of greater intersexual than intrasexual overlap; this differs from many other carnivore studies. Movements of individuals and distribution of den sites indicated that striped skunks, irrespective of sex or size, prefer edge habitat in comparison to forest or field.

Sibling rivalry seems to contradict Hamilton's rule of maximizing inclusive fitness (Hamilton, 1964). However, when critical resources are scarce and the competitors are close kin the individual must weigh the direct versus the indirect components of its inclusive fitness (Mock & Parker, 1997). In facultatively siblicidal species, conflicts arise mainly because of the phenomenon of ‘parental optimism’, in which the parents attempt to raise a larger brood than the average amount of expected resources allow (Lack, 1954; Temme & Charnov, 1987; Mock & Forbes, 1995). If critical resources are low, weaker or subordinate offspring may be killed by a stronger or dominant sibling. Sibling mortality may result from direct physical damage and/or socially enforced starvation (Mock, 1984).

In a recent paper, Dawson et al. (1999) investigated how the morphology of the contour and downy afterfeathers of gentoo penguins Pygoscelis papua function as thermal insulators. Their model considered how the morphology of individual feather barbs interact to create an efficient insulatory barrier. They noted that, during diving, the feathers must be compressed and return to their original configuration due to stored strain energy. In addition, the downy feathers of penguins have to withstand significant wind loading whilst the birds are on land (Taylor, 1986). Despite the obvious necessity for mechanical competence and resilience of down feathers, we still know little about their mechanical performance.

The cheetah Acinonyx jubatus is an atypical felid, well known for having blunt, only slightly curved, and only partly retractile claws, clearly an adaptation for high-speed locomotion in the pursuit of swift mammals. However, saying that prey ‘is usually knocked down by the force of the cheetah's charge’ (Nowak, 1999) is incorrect, because this predator actually relies on the claw of the first digit of the forepaw, the so-called dewclaw, to hook the fleeing prey off balance. Although (1) this was understood by Indian huntsmen through their use of tame cheetahs and published (Burton, 1950) in a natural history journal circulating well outside India, (2) wounds attributable to the dewclaws of cheetahs were later observed (Schaller, 1972) on prey animals in Africa, the area of most research on this felid, and (3) the information from India was finally reported (though with the wrong year in the citation) in an authoritative book on African mammals (Kingdon, 1977), no systematic study of the dewclaw itself, or of explicitly related questions, has been made. Perhaps the general connotation of the term ‘dewclaw’, as intended for a non-functional claw on a rudimentary digit as in the case of dogs, has masked the importance of what is not only a strongly curved and sharply pointed, but also a very large claw in the cheetah. In fact, this specialization of the cheetah has escaped the attention of behaviourists (Eaton, 1970), anatomists (Gonyea & Ashworth, 1975), and palaeontologists (Adams, 1979).

Tooth succession was followed in captive greater cane rats Thryonomys swinderianus of known ages with the aid of regular radiographs. The incisors and single premolar tooth (dP 4/4) in each quadrant are persistent deciduous teeth that are not replaced by permanent teeth. Tooth succession is relatively slow, with eruption of the lower cheek teeth in advance of the upper ones. During the first 5 months of post-natal development, three cheek teeth per quadrant become functional. Another 5 months elapse before the fourth cheek tooth erupts. The same slow growth can be seen in the increase in mass, which only doubles 5 months after puberty (5 months).