This study investigated how demographic characteristics of black rat snakes Elaphe obsoleta are affected by the length of the active season, and also used the resulting demographic data to determine the proximate factors responsible for male-biased sexual size dimorphism (SSD) in the species. Demographic data collected from 1981 to 1998 in Ontario (ON; 583 males and 588 females) and from 1942 to 1976 in Maryland (MD; 180 males and 150 females) were used to develop growth models with the von Bertalanffy growth equation. Instantaneous growth rates declined significantly with increasing snout–vent length (SVL) in males and females of each population. The growth models predicted age using SVL satisfactorily, but the accuracy of the model decreased significantly with increasing SVL. As predicted, based on the brevity of their active season (ON [ape ] 135 days, MD [ape ] 190 days), rat snakes of both sexes from Ontario had lower and more variable instantaneous growth rates and matured at a more advanced age (ON [ape ] 9 years, MD [ape ] 4 years) than snakes from Maryland. However, the rapid growth and early maturation in Maryland snakes occurred at the expense of longevity (maximum: ON [ape ] 30 years, MD [ape ] 20 years). Slower growth and later maturation will make rat snakes in Ontario less capable of recovering from population declines. Within each population, males grew faster than females. Survivorship for Ontario snakes did not vary by sex, but increased significantly with increasing SVL. The demographic consequence of sex differences in growth was a male-biased sex ratio among larger snakes. Because SSD is a function of males growing faster than females, SSD in black rat snakes is probably a product of sexual selection, suggesting that large size confers a mating advantage in males.

The aim of this study was to investigate the effect of food deprivation on the cardiac activity of two Mediterranean limpets, the exploiter Patella caerulea and the conserver P. rustica, which have different foraging regimes. Heart rate variations were monitored in the two species according to two experimental protocols: (1) starvation/recovery, during which limpets were starved for up to 15 days and then allowed to feed on boulders covered with microalgae; (2) starvation/forced feeding, during which specimens were starved for 11 days and then fed orally with a test (30 mg/ml glucose) or control solution. Increasing starvation time was associated with a significant decline of heartbeat frequency in both species. The decline was comparable in the two species, but heartbeat frequencies in P. rustica were always significantly lower than in P. caerulea. When the limpets were allowed to feed on natural substrates, a rapid increase in heart rate was observed, with frequencies slightly higher than those measured at the beginning of the experiment. No significant difference in heart rate was observed between the two species. Similarly, both in P. caerulea and P. rustica forced feeding caused a recovery of heart rate to pre-treatment levels. The results are consistent with previous findings on the metabolic consequences of food deprivation in gastropods and demonstrate the ability of both species to depress their heart rate when faced with a food shortage. Moreover, a greater regulative ability was observed in P. rustica than in P. caerulea, confirming their status as conserver and exploiter, respectively.

The Madeiran land snail genus Heterostoma contains two taxa distinguished by differences in genital anatomy: one has full hermaphroditic genitalia (euphallic) while the other lacks the distal male organs (hemiphallic). Snails from the Madeiran islands of Porto Santo and Ilhéu de Cima were kept under controlled conditions differing in humidity and simulated rainfall. There were four treatments: (1) low humidity, no rainfall; (2) low humidity, rainfall; (3) high humidity, no rainfall; (4) high humidity, rainfall. For snails from Porto Santo there were viability differences between taxa under all treatments such that hemiphallics were most viable under treatment 1 and euphallics were more viable under all other treatments. There were no significant differences between taxa taken from Ilhéu de Cima. This may be a real effect or the result of smaller sample size or a combination of both. Under all conditions, both taxa from both islands show a time-dependent reduction in viability in response to rainfall. Taxa from Porto Santo also respond differently to humidity with hemiphallics surviving for less time than euphallics at high humidity. These results are interpreted as showing a difference in physiological tolerance between taxa from Porto Santo with respect to humidity. It is suggested that this ecological difference may have been a factor in the divergence of the taxa, perhaps through interaction with genital anatomy variation. No firm conclusions can yet be drawn regarding samples taken from Ilhéu de Cima.

Agonistic and sexual interactions as well as plasma bioactive luteinizing hormone (LH) concentrations were monitored in all the adults of two colonies of the naked mole-rat Heterocephalus glaber at three phases in the pregnancy of the breeding female. Blood samples were collected at early (days 1–15), mid (days 30–40) and late (days 55–65) phases of her pregnancy, and the circulating basal plasma LH and the response to administration of 0.1 μg gonadotrophin-releasing hormone (GnRH) were examined. In both colonies it was found that non-breeding males and females showed depressed basal LH concentrations and responses to a GnRH challenge. However, there was considerable variation between individuals, in terms of both basal plasma and post-GnRH concentrations of LH, implying that certain individuals were more suppressed than others. The responses were more pronounced in non-breeding males than in non-breeding females, and this is discussed in light of the reproductive skew occurring within colonies. Few agonistic interactions occurred between the breeding female and the majority of the colony members, and overall, there was no clear relationship between plasma LH and the amount of aggression received from the breeding female. However, in one colony there was a significant positive correlation between basal plasma LH concentrations of non-breeding females and agonistic interactions received by them from the breeding female. In this same colony, older females and older and heavier males received most of the aggression from the breeding female. The second colony did not show this trend, possibly because it had recently lost many large animals during fighting for succession; in this colony sexual interactions were elevated.

The brush-tailed porcupine Atherurus africanus is an important source of meat for local people in tropical forested areas of Central Africa. Information on the biology of this species in free-ranging conditions is scarce. Data on its reproduction and productivity are essential to establish accurate management practices in the exploitation of this rodent. In order to provide data on the reproductive physiology and to assess the prolificacy of the brush-tailed porcupine in the wild, the structural and functional anatomy of the ovaries of free-ranging females were studied. Twenty-two female carcasses were obtained from various markets in Libreville, Gabon, between August 1995 and February 1997. Reproductive tracts were macroscopically examined for the presence of embryos or foetuses. The ovaries were embedded in paraffin wax or plastic and examined by light microscopy. The morphology and constituent cell types of the ovaries were similar to those described for other hystricognath rodents. All pregnant females had only one embryo or foetus and the number of corpora lutea (CL) per female was 19.9 ± 5.4 (mean diameter ± sd, 1709 ± 421 μm), including one CL of pregnancy (diameter, 4821 ± 1364 μm). Also, 8.9 ± 6.8 accessory CL per female in the pre-implantation and embryonic stages of pregnancy (diameter, 1629 ± 463 μm) were observed. The average active luteal volume was high (115.6 ± 73.5 mm3). The mean number of antral follicles in the adult females was 24.6 ± 9.9. The study confirms that the brush-tailed porcupine is a mono-embryonic species, as observed in captive breeding experiences, but polyovular, suggesting important ovum mortality. This unusual reproductive feature in a mammalian species gives this rodent a low reproductive productivity. Therefore, A. africanus could be more susceptible to the effects of hunting than generally thought.

Plio-Pleistocene suid assemblages of sub-Saharan Africa seem to have been derived from the immigration of Asian tetraconodontines during the late Miocene and of Asian suines in the mid Pliocene. Lineages of both subfamilies display evolutionary changes that decrease the length of the premolar row and increase the length, height and complexity of the molars. Such changes have proved useful for estimating the relative ages of the sites from which suid fossils have been retrieved. They have also been used for interpreting the probable habitat and as evidence of environmental change through time. Isotopic analyses of tooth enamel from extant suid species generally confirm field observations of their dietary preferences. Similar analyses of suid dental enamel from Neogene localities of eastern Africa provide information that partly supports previous interpretations of the diets of extinct suid species. The increase in size and complexity of nyanzachoere teeth reflects their exploitation of C4 vegetation, although the nyanzachoeres did not acquire their grazing habits until after contemporary perissodactyls and proboscideans had become dedicated C4 grazers. In contrast to earlier interpretations, kolpochoeres and metridiochoeres were already dedicated grazers by the time they became significant components of the East African biota. Like their living counterparts, the warthogs and forest hogs, metridiochoeres were less water-dependent than kolpochoeres.

Bats seldom soar because it is behaviour generally associated with the use of thermals, which are normally of insufficient strength at night to support the behaviour. Daylight flying bats, however, such as the Samoan flying fox Pteropus samoensis may be able to exploit thermals for soaring. This may give the bats one of two advantages. It may reduce the energy costs of transport because gliding flight is much cheaper than active flapping flight. However, because less endogenous heat is generated by soaring, a second advantage may be that it reduces the thermal stress placed on these bats. Thermal stress is a factor that we have shown previously probably constrains the daylight flying behaviour of this species. Observations of the patterns of soaring behaviour at two sites on American Samoa in March and October 1995 supported the predictions of the energy saving but not the hyperthermia avoidance hypothesis. Soaring was a common behaviour under all conditions and was used extensively when conditions did not pose a threat of hyperthermia. In March, the bats also adopted flight patterns over time that exposed them to areas of the valleys where insolation was greatest, presumably increasing their risk of hyperthermia but bringing energy saving benefits. Modelling the expected heat flows during soaring and flapping flight using an established model revealed that soaring reduced the risk of hyperthermia, when flying in the shade of clouds, because of the energy savings resulting from reduced endogenous heat production. However, when soaring in sunlight, these savings are more than offset by the increased exogenous heat uptake, because a greater proportion of the wing surface is exposed when soaring. Despite its low endogenous energy cost, soaring in sunlight is not thermally advantageous, and the behaviour of the bats reflected this fact.

The free-ranging feeding behaviours of five adult koalas Phascolarctos cinereus with varying degrees of tooth wear were investigated using acoustically sensitive radio telemetry. An increase in tooth wear was found to be associated with a significant increase in the average amount of time spent feeding, average number of leaves consumed and the average number of daily chews. This suggests that koalas compensate for tooth wear by increasing food intake. Furthermore, there was a significant increase in the average number of chews per leaf and average chew rate, suggesting a greater investment in processing each leaf.

In the holm oak Quercus ilex dehesas of the Iberian Peninsula, several food types occur that can be selected by birds through the winter. In this framework, diet composition and diet selection of common cranes Grus grus was studied during a rainy wintering season. The winter diet of the common crane is mostly herbivorous in the holm oak dehesas of south-west Spain with <10% of items being of animal origin. Leaves and stems of sown cereal, bulbs, acorns and cereal grain are the most common vegetable food types. The diversity of the overall winter diet was similar among juveniles and among adults with and without juveniles in attendance. However, there were differences in diet composition between juvenile birds and their parents. Furthermore, the diet composition of adult cranes with juveniles in attendance was different from that of adult cranes without juveniles in attendance. Foraging abilities of juvenile cranes did not vary significantly through the winter, suggesting a low effect of experience on diet differences between age classes. Our results point toward the existence of diet differences among the three considered crane categories related with differential habitat selection by family groups. The monthly pattern of choice of each food type differed from those expected according to the monthly pattern of food availability in the study area. Cereal grain was the most preferred food type when it was available. When cereal seed germinated, cranes shifted to acorns and bulbs which were then more profitable.

Twenty-one cat owners from a 100 km2 area, centred on Carnforth, Lancashire, England, recorded each dead prey item delivered by their cat or cats during an 8-week period, following one of three experimental schedules, each of which required each cat to have a bell on a collar for only half of the time. The mean number of items each cat delivered to the owner was 2.9 in the 4 weeks when the cats had a bell attached, compared to 5.5 for the equivalent time when the bell was absent. The bell had no effect on the relative numbers of different prey types delivered, and there was no evidence that the cats adapted their hunting behaviour to reduce the effect of the bell over time.

Some aspects of the colony and social structure of the Ghana mole-rat Cryptomys zechi were studied in a mesic Guinea savanna woodland in Ghana. Colony size ranged between one and seven (average 3.6). The mean adult body weight was 217.9 g and the colony biomass was 634 g. Responsibility for colony safety in C. zechi, as revealed from order of capture in response to damage to the burrow system, is age dependent, with sub-adults being the most frequent repairers. There are indications that male workers are more involved in colony maintenance than females and that the reproductive individuals, especially the males, perform little work. We discuss the finding that C. zechi although a social bathyergid, is close to the bottom of the sociality ladder.

The opportunity for selection, I, calculated as the variance in relative fitness, sets an upper limit to the amount of adaptive change that selection may produce. Therefore, it is a potentially valuable, and frequently used, measure of the potential of action of phenotypic selection. Although many different aspects of I calculation and analysis have been explored, the effect of the spatial scale chosen for calculation received little attention, notwithstanding the growing evidence that natural populations are not homogeneous and present a hierarchical spatial structure. The effect of scale on the estimation of I was examined from data collected in two populations of southern elephant seals (Mirounga leonina), an easily observable and strongly polygynous species. A significant effect of spatial scale on three important aspects of I calculation and analysis was found: dependence of I on mean fitness, between population variation of I, and effect of local demography on I.

The Channel Island of Jersey is 116 km2 but has only 540 ha of woodland distributed in 237 wooded fragments with mean size of 2.5 ha. Despite this, the island supports 300 to 600 red squirrels Sciurus vulgaris, a species that is under threat in mainland Britain from habitat fragmentation, disease and the spread of the alien grey squirrel S. carolinensis. Grey squirrels are not present on Jersey. Between 1994 and 1997, using trapping and tracking techniques, we studied how red squirrels survive on Jersey by focusing on three local populations in sites B, C and S with contrasting food availability. The primary squirrel foods at site B were autumn tree seeds, at site C autumn tree seeds and summer conifer cones, and at site S autumn tree seeds and ad libitum, year-round supplementary food provided by local people. The densities of squirrels in site C (mean over 3 years 0.97 ha−1) and site S (1.21 ha−1) were more than one and a half times that of site B (0.68 ha−1), which relied on autumn seeds. Body mass and condition, and early breeding (spring litters) were not affected by food availability although conception occurred as early as November, earlier than in mainland Britain. Less than 50% of females produced summer litters, and 88% of non-breeders did not receive supplementary food. Turnover rates were lowest and most stable in site B. Annual residency was not influenced by the size of the natural tree seed crop. Cat and road kills caused two out of three reported deaths. This island population seems to remain viable as a result of an extended breeding season and increased population densities in sites with summer or supplementary food. The results emphasize the beneficial effects of extra food provided by local people. This provides a buffering effect against variations in natural food availability, and seems to be important for their long-term survival.

Female Cape ground squirrels Xerus inauris live in matrilineal kin groups in which the number of reproductive positions is limited to three females. Field observations on a population in Namibia revealed that the mechanisms by which group size was limited were reproductive suppression and group fission. Sub-adult females attained sexual maturity at 8 months of age when only a single adult female was present in their social group, whereas sub-adult females in groups with more than one adult female matured at 12 months of age. Social groups with more than three breeding females subsequently split into smaller groups. Several hypotheses for limiting group size were considered. There was no evidence of higher ectoparasite loads on females in larger groups, nor was survival of adult females affected by group size. Although adult females have lower body masses and higher mortality during the winter when food is more scarce, feeding competition alone does not seem to limit group size. Groups that split continued to overlap in their feeding ranges and there was no seasonal difference in juvenile survival. However, juvenile survival was affected by group size. The greatest cost of being in a larger group was lower juvenile survival. Larger groups use larger feeding ranges, and because squirrels return to their sleeping burrow when threatened, not just to the nearest refuge, slower juveniles have greater exposure to predators. Thus, although competition for food resources may be important, predation seems to be a major constraint on female group size as well as the primary selective force leading to female group formation.

Between 1987 and 1996 the numbers of badgers Meles meles in Wytham Woods rose from 60 to 228 adults. The area occupied by the population has not changed and thus density has also risen from 10 adult badgers/km2 to 38/km2. This rise parallels an increase in badger abundance seen across Britain in recent years. The hypothesis that this increase is either the consequence of improved badger protection or of changes in habitat can be rejected for this site. Instead, a link between increasing numbers and changing weather patterns, possibly resulting from climate change, is investigated. In particular, attention is drawn to a correlation between mild winters and heavier body weights of badgers in January. Furthermore socio-spatial restructuring within the population may be the mechanism that has permitted high density to be sustainable. The increase in badger numbers at Wytham has not affected population sex ratio, which has remained relatively constant at parity throughout the study.

INTERNATIONAL COMMISSION ON ZOOLOGICAL NOMENCLATURE

The following Applications were published on 29 June 2001 in Volume 58, Part 2 of the Bulletin of Zoological Nomenclature. Comment or advice on any of these Applications is invited for publication (subject to editing) in the Bulletin and should be sent to the Executive Secretary, International Commission on Zoological Nomenclature, c/o The Natural History Museum, Cromwell Road, London SW7 5BD, U.K. (e-mail: [email protected]).