Temporal Changes in Population Dynamics of American Martens

ABSTRACT Population parameters of American martens (Martes Americana) are often monitored to guide management actions. In order to better understand changing marten population demographics, we estimated marten abundance and several population parameters on a portion of northeast Chichagof Island (NCI), Southeast Alaska, USA, using capture-mark–recapture methods in combination with radiotelemetry and compared these data with demographic estimates derived from the trapper catch from the larger NCI area. We found that capture probability remained relatively high across trapping sessions by using a standard live-trapping protocol, and we found no evidence of capture probability being consistently affected by population or environmental factors. Estimated marten numbers varied greatly over the period, ranging from a low of 14.1 martens (0.17/km²) during winter 1997–1998 to a high of 45.6 martens (0.55/km²) during winter 1995–1996. The annual trend was for decreasing numbers from winter 1990–1991 to winter 1992–1993, then increasing numbers through winter 1995–1996. By winter 1996–1997, numbers had dropped substantially and remained low through 1997–1998. All population parameters varied temporally, including annual survival (0.34–1.00), sex ratio (1.0–3.5), mean age (0.5–2.9), body condition (-0.08–1.35), and fecundity (0.44–2.70). Yearly trapper catches on NCI varied greatly from 19 to 354 martens (0.02 martens/km² to 0.31 martens/km²) because of changing trapper effort and marten abundance. We found mean ages of carcasses a good predictor of population mean age, but sex ratios were highly variable. Marten numbers and fecundity were strongly correlated with rodent abundance, especially long-tailed voles (Microtus longicaudus). By monitoring demographic parameters of the population or trapper-caught carcasses, managers can gain insight into temporal population dynamics. Also, total captures of individuals may provide a useful estimate of marten numbers without the expense of radiocollaring and tracking individuals because population estimates were highly correlated with number of individuals captured during a standard survey. Because of their high vulnerability to trapping, close monitoring of marten populations is important for the conservation and sustained-yield management of the species. A tracking strategy developed with input data on preseason abundance and age structure may be the best management approach, especially for small populations with limited immigration.     

Specific visualization of tubulin-containing structures in tissue culture cells by immunofluorescence. Cytoplasmic microtubules, vinblastine-induced paracrystals, and mitotic figures.

Antibody against tubulin from the outer doublets of sea urchin sperm flagella reacts with tubulin-containing structures in mammalian cells. Thus cytoplasmic microtubules, vinblastine-induced paracrystals and the full spectrum of mitotic figures can be visualized by immunofluorescence. These results show that the tubulin structure has been highly conserved during evolution.     

Circumfacial Markings in Siamang and Evolution of the Face Ring in the Hylobatidae

The occurrence of a white brow band in siamang is documented for the first time. The characteristic occurs in 4.4% of 250 siamang. Among adult siamang the characteristic occurs more often in females than in males (11.3% of 71 females vs. 1.4% of 73 males). In a particular family lineage of captive siamang (not included in the numbers above), the characteristic was unusually frequent (42.9% of 14). The trait appears to be inherited, possibly as an autosomal dominant inheritance. Additional white markings occur in at least one of the subjects on hands, feet, and in a corona above the ears. In contrast to other studies, our results suggest that the presence of white facial markings, and possibly also of white hands and feet and of a bright corona are primitive gibbon traits. In addition, some degree of sexual dichromatism in the circumfacial markings appears to have occurred in the common ancestor of all gibbons.     

GROWTH RATES OF ANTARCTIC FUR SEALS AS INDICES OF ENVIRONMENTAL CONDITIONS

The growth rates of Antarctic fur seal ( Arctocephalus gazella ) pups estimated from weighing cross-sections of the population were compared with measured/ inferred changes in the availability of their main prey species, Antarctic krill ( Euphausia superba ) from 1989 to 2000. There was no relationship between growth rate and mass at weaning and there were counter-intuitive indications of higher growth rates in years of low krill availability. Biases reflecting changes in the component of the population available for sampling appear to invalidate the widely held assumption that interannual differences in growth rate can reliably be derived from differences in the slope of a linear relationship based on cross-sectional population samples. A new index was developed, based on the deviation of pup mass at age in each year compared to the multiyear mean, that was not dependent on assumptions of linearity. The indices of growth deviates produced a more logical relationship with other indices of pup development and related more appropriately to variations in prey availability. The potential impact of methodological biases on the interpretation of growth rate suggests that comparisons of growth rates should not rely on assumptions regarding the underlying growth pattern.     

Activity‐specific metabolic rates for diving,transiting, and resting at sea can be estimated from time–activity budgets in free‐ranging marine mammals

Time and energy are the two most important currencies in animal bioenergetics. How much time animals spend engaged in different activities with specific energetic costs ultimately defines their likelihood of surviving and successfully reproducing. However, it is extremely difficult to determine the energetic costs of independent activities for free‐ranging animals. In this study, we developed a new method to calculate activity‐specific metabolic rates, and applied it to female fur seals. We attached biologgers (that recorded GPS locations, depth profiles, and triaxial acceleration) to 12 northern (Callorhinus ursinus) and 13 Antarctic fur seals (Arctocephalus gazella), and used a hierarchical decision tree algorithm to determine time allocation between diving, transiting, resting, and performing slow movements at the surface (grooming, etc.). We concomitantly measured the total energy expenditure using the doubly‐labelled water method. We used a general least‐square model to establish the relationship between time–activity budgets and the total energy spent by each individual during their foraging trip to predict activity‐specific metabolic rates. Results show that both species allocated similar time to diving (~29%), transiting to and from their foraging grounds (~26–30%), and resting (~8–11%). However, Antarctic fur seals spent significantly more time grooming and moving slowly at the surface than northern fur seals (36% vs. 29%). Diving was the most expensive activity (~30 MJ/day if done non‐stop for 24 hr), followed by transiting at the surface (~21 MJ/day). Interestingly, metabolic rates were similar between species while on land or while slowly moving at the surface (~13 MJ/day). Overall, the average field metabolic rate was ~20 MJ/day (for all activities combined). The method we developed to calculate activity‐specific metabolic rates can be applied to terrestrial and marine species to determine the energetic costs of daily activities, as well as to predict the energetic consequences for animals forced to change their time allocations in response to environmental shifts.     

Stable isotopes document seasonal changes in trophic niches and winter foraging individual specialization in diving predators from the Southern Ocean

1. Climatic variation outside the breeding season affects fluctuations in population numbers of seabirds and marine mammals. A challenge in identifying the underlying biological mechanisms is the lack of information on their foraging strategies during winter, when individuals migrate far from their breeding grounds. 2. We investigated the temporal variability in resource partitioning within the guild of five sympatric Subantarctic penguins and fur seals from Crozet Islands. The stable isotopic ratios of carbon (delta(13)C) and nitrogen (delta(15)N) for whole blood were measured for penguins and fur seals, as were the isotopic ratios for penguin nails and food. Animals were sampled at two periods, during breeding in summer and at their arrival in the colonies in spring (hereafter winter, since the temporal integration of blood amounting to several months). 3. In summer, delta(13)C and delta(15)N for blood samples defined three foraging areas and two trophic levels, respectively, characterizing four nonoverlapping trophic niches. King penguins and female Antarctic and Subantarctic fur seals are myctophid eaters foraging in distinct water masses, while both macaroni and rockhopper penguins had identical isotopic signatures indicating feeding on crustaceans near the archipelago. 4. Isotopic ratios were almost identical in summer and winter suggesting no major changes in the species niches, and hence, in the trophic structure of the guild during the nonbreeding period. A seasonal difference, however, was the larger variances in delta(13)C (and also to a lesser extent in delta(15)N) values in winter, thus verifying our hypothesis that trophic niches widen when individuals are no longer central place foragers. 5. Winter isotopic ratios of macaroni penguins and male Antarctic fur seals had large variances, indicating individual foraging specializations. The range of delta(13)C and delta(15)N values of male fur seals showed, respectively, that they dispersed over a wide latitudinal gradient (from Antarctica to north of the archipelago) and fed on different prey (crustaceans and fish). 6. By comparing summer and winter isotopic ratios and examining the summer diet, we highlight the feeding habits of marine predators that were not previously addressed. The findings have a number of implications for understanding the functioning of the pelagic ecosystem and on the demography of these species.     

东方田鼠的游泳行为和能力

东方田鼠(Microtus fortis)是一种栖息于湿地生境的小型哺乳动物,为了解其水生运动适应,作者在实验室内观察和测试了该鼠的游泳行为、皮毛防水性能和长时间游泳能力。结果发现,东方田鼠主要在水面游泳,亦能潜水,游泳姿势是狗刨式,并主要以后肢交替划水提供推进力,速度约为0.37 m/s。在20℃水温条件下,东方田鼠皮毛表现出良好的防水性能,且防水性能与其年龄及体重均存在极显著的负相关关系(P 0.01,R~2=0.805);东方田鼠具有平均约持续5 h以上的长时间游泳能力,且长时间游泳能力与其皮毛防水性能存在极显著的正相关关系(P 0.01,R~2=0.682);上述两项指标性别差异显著。这表明,东方田鼠有较强的水中运动能力和长时间游泳能力,具有水生运动方面的适应性进化,有利于其在沼泽等栖息地的生存。     

Response to capture stress involves multiple corticosteroids and is associated with serum thyroid hormone concentrations in Guadalupe fur seals (Arctocephalus philippii townsendi)

Guadalupe fur seals are a threatened species with few breeding locations, which potentially makes them sensitive to environmental or anthropogenic stressors. We present the first study to quantify adrenal and thyroid function in this species in an effort to measure their stress response to capture. We analyzed a suite of corticosteroid hormones released over time during capture in both adult females (n = 10) and weanling pups (n = 26) during March 2016. Multiple corticosteroids were released during capture, and aldosterone was associated with the response to stress in adults only. These results suggest the regulation of aldosterone secretion in association with the HPA axis in otariids as reported in other marine mammals. Individuals varied markedly in the magnitude of their endocrine response to capture. A lower total integrated stress response to capture for both cortisol and corticosterone was associated with decreased concentrations of thyroid hormone T3 and elevated concentrations of reverse T3 (rT3), suggesting parallel downregulation of adrenal and thyroid endocrine axes in some individuals. A scaled body condition index was negatively associated with T3 and positively associated with rT3 in adults. Together these findings suggest utility in using endocrine responses to capture stress to evaluate individual and population health.     

Foraging a new trail with northern fur seals (Callorhinus ursinus): Lactating seals from islands with contrasting population dynamics have different foraging strategies,and forage at scales previously unrecognized by GPS interpolated dive data

We reconstructed the foraging tracks of lactating northern fur seals (Callorhinus ursinus) from two eastern Bering Sea islands (St. Paul Island and Bogoslof Island) using linear interpolation between GPS locations recorded at a maximum of four times per hour and compared it to tri‐axial accelerometer and magnetometer data collected at 16 Hz to reconstruct pseudotracks between the GPS fixes. The high‐resolution data revealed distances swum per foraging trip were much greater than the distances calculated using linearly interpolated GPS tracks (1.5 times further for St. Paul fur seals and 1.9 times further for Bogoslof fur seals). First passage time metrics calculated from the high resolution data revealed that the optimal scale at which the seals searched for prey was 500 m (radius of circle searched) for fur seals from St. Paul Island that went off‐shelf, and 50 m for fur seals from Bogoslof Island and surprisingly, 50 m for fur seals from St. Paul that foraged on‐shelf. These area‐restricted search scales were significantly smaller than those calculated from GPS data alone (12 km for St. Paul and 6 km for Bogoslof) indicating that higher resolution movement data can reveal novel information about foraging behaviors that have important ecological implications.