REPRODUCTION IN THE FEMALE SUBANTARCTIC FUR SEAL, ARCTOCEPHALUS TROPICALIS

The reproductive tracts of 89 female subantarctic fur seals, taken at Gough Island between November 1977 and October 1978, were examined. Females started ovulating at age 4 yr and all 6-yr-old females were sexually mature. They are mono-ovulatory, alternating between ovaries, and only single embryos were found. Females older than 13 yr ( n = 11) showed poor follicular development and some failed to ovulate. The gestation period (first recorded ovulation to first recorded birth) was 360 d, while delayed implantation (first recorded ovulation to first recorded implantation) lasted for 139 days. Follicle numbers in the functional ovary declined sharply after ovulation while the corpus luteum increased in size until at least 1 mo prior to parturition. The number of follicles in the contralateral ovary increased after midwinter (June/July), and the mean size of the largest follicles peaked prior to ovulation in December. The mean size of the largest follicles increased in both ovaries near implantation time, after reaching a low subsequent to, ovulation. The regressing corpus albicans, conspicuous for approximately 3 mo after parturition, could not be detected macroscopically within one year postpartum. Subantarctic fur seals at Gough Island have a distinct postreproductive class of older females. The pregnancy rate for all females ≥4 yr of age was 79%, and it was 84.5% for the sexually mature group of ≥6 yr of age, while the mean age at puberty was 4.80 yr.     

Population-level impacts of natural and anthropogenic causes-of-death for Hawaiian monk seals in the main Hawaiian Islands

Identifying, assessing, and ranking the impact of individual threats is fundamental to the conservation and recovery of rare and endangered species. In this analysis, we quantify not only the frequency of specific causes-of-death (CODs) among Main Hawaiian Island (MHI) monk seals, but also assess the impact of individual CODs on the intrinsic growth rate, λ, of the MHI population. We used gross necropsy results, histopathology, and other evidence to assign probabilities of 11 COD types to each mortality and then used Monte Carlo sampling to evaluate the influence of each COD on λ. By right censoring realizations involving specific CODs, we were able to estimate λ (and its associated uncertainty) when CODs were selectively removed from influencing survival. Applying the analysis to all known and inferred deaths believed to have occurred 2004–2019, the CODs with the largest influence on λ were anthropogenic trauma, anthropogenic drowning, and protozoal disease. In aggregate, anthropogenic CODs had a larger effect on the growth rate than either natural or disease CODs. Possible bias associated with differential carcass detection, recovery, and COD classification are discussed.     

USE OF BIOELECTRICAL IMPEDANCE ANALYSIS TO ASSESS BODY COMPOSITION OF SEALS

Abstract: Bioelectrical impedance analysis (BIA) measures resistance and reactance of a current as it passes through an organism. The validity of using BIA as a tool to measure body water content, and hence body composition and condition, was tested on harp and ringed seals. The resistance and reactance readings from BIA were compared to estimates of total body water (TBW) determined via tritiated water dilution. The relationship between resistance and TBW (% of body mass) was linear after logarithmic transformation and the two variables were highly correlated. We describe the electrode configuration and placements which provide reliable results in these seals. Our findings indicate that BIA has considerable potential as an inexpensive, rapid, and reliable technique for estimating body composition of phocid seals.     

Individual variation in pup vocalizations and absence of behavioral signs of maternal vocal recognition in Weddell seals (Leptonychotes weddellii)

Individually stereotyped vocalizations often play an important role in relocation of offspring in gregarious breeders. In phocids, mothers often alternate between foraging at sea and attending their pup. Pup calls are individually distinctive in various phocid species. However, experimental evidence for maternal recognition is rare. In this study, we recorded Weddell seal (Leptonychotes weddellii) pup vocalizations at two whelping patches in Atka Bay, Antarctica, and explored individual vocal variation based on eight vocal parameters. Overall, 58% of calls were correctly classified according to individual. For males (n= 12) and females (n= 9), respectively, nine and seven individuals were correctly identified based on vocal parameters. To investigate whether mothers respond differently to calls of familiar vs. unfamiliar pups, we conducted playback experiments with 21 mothers. Maternal responses did not differ between playbacks of own, familiar, and unfamiliar pup calls. We suggest that Weddell seal pup calls may need to contain only a critical amount of individually distinct information because mothers and pups use a combination of sensory modalities for identification. However, it cannot be excluded that pup developmental factors and differing environmental factors between colonies affect pup acoustic behavior and the role of acoustic cues in the relocation process.     

Sink or swim: Risk stratification of preweaning mortality in harbor seal pups (Phoca vitulina richardii) admitted for rehabilitation

To date, few consistent relationships between survival in rehabilitation programs and diagnostic measures recorded upon admission have been identified for harbor seal pups. Veterinary records for 718 unweaned Pacific harbor seal pups (Phoca vitulina richardii) admitted to a rehabilitation center were examined to identify clinical factors associated with preweaning survival and develop a triage tool to stratify pups according to their risk of mortality. Physical, serum chemical, and hematological variables were examined and their relationship with survival to weaning was assessed by logistic regression and classification and regression tree (CART) analysis. Survival to weaning was 85.1% and many clinical variables reflecting the pups’ age, size, growth, injuries, and blood parameters were associated with the likelihood of survival. A decision tree model, consisting of serum concentrations of phosphorus, sodium, and calcium, successfully stratified harbor seal pups into clinical subgroups according to their preweaning mortality risk. For both the derivation and validation cohorts, pups classified as “high risk” had significantly lower odds of survival, while those classified as “low risk” had significantly greater odds of survival. This simple decision tree could serve as a practical triage tool to help identify and direct care towards pups at higher risk of preweaning mortality.     

Modelling broad‐scale wolverine occupancy in a remote boreal region using multi‐year aerial survey data

Aim

We used data from aerial surveys of wolverine tracks collected in seven winters over a 10‐year period (2003–2012) within a 574,287 km² study area to evaluate the broad‐scale pattern of wolverine occurrence across a remote northern boreal forest region, identifying areas of high and low occupancy.

Location

Northern Ontario, Canada.

Taxon

Wolverine (Gulo gulo Linnaeus, 1758).

Methods

We collected wolverine tracks and observations in 100‐km² hexagonal survey units, making a total of 6,664 visits to 3,039 units, visiting each 1–9 times. We used hierarchical Bayesian occupancy modelling to model wolverine occurrence, and included covariates with the potential to affect detection and/or occupancy probability of wolverines.

Results

we detected wolverines on 946 visits, 14.2% of total visits. Probability of detecting a wolverine varied among years and between the two ecozones in the study area. Wolverine occupancy was negatively related to two important covariates, the geographical coordinate Easting and thawing degree‐days. A site occupancy probability map indicated that wolverine occupancy probabilities were highest, and standard error lowest, in the western and northern portions of the study area.

Main conclusions

The occupancy framework enabled us to use observation data from tracks of this elusive, wide‐ranging carnivore over a vast, remote area while explicitly considering detectability and spatial autocorrelation, yielding a map of probable wolverine distribution in northern Ontario that would not be possible using other methods of detection across a large region. With resource development pressures increasing in this globally significant region in the face of a changing climate, it is important to monitor changes in distribution of species like wolverines that have low population growth rates, large spatial requirements and sensitivity to human disturbance. This study demonstrates a relatively cost‐effective and non‐invasive alternative to monitoring based on wolverine harvest records, which have not been available since 2009 in Ontario due to changes in the provincial regulatory regime for this threatened species.     

Identifying QTL and genetic correlations between fur quality traits in mink (Neovison vison)

Mapping of QTL affecting fur quality traits (guard hair length, guard hair thickness, density of wool, surface of the fur and quality) and skin length was performed in a three‐generation mink population (F₂ design). In the parental generation, Nordic Brown mink were crossed reciprocally with American Black short nap mink. In all, 1082 mink encompassing three generations were used for the analyses. The mink were genotyped for 104 microsatellites covering all 14 autosomes. The QTL analyses were performed by least‐square regression implemented in gridqtl software. Genetic and phenotypic correlations and heritabilities were estimated using the average information‐restricted maximum‐likelihood method. Evidence was found for QTL affecting fur quality traits on nine autosomes. QTL were detected for guard hair thickness on chromosomes 1, 2, 3, 6 and 13; for guard hair length on chromosomes 2, 3 and 6; for wool density on chromosomes 6 and 13; for surface on chromosomes 7, 12 and 13; for quality on chromosomes 6, 7, 11 and 13; and for skin length on chromosomes 7 and 9. Proximity of locations of QTL for guard hair length, guard hair thickness and for wool density and quality suggests that some of the traits are in part under the influence of the same genes. Traits under the influence of QTL at close or identical positions also were traits that were strongly genotypically correlated. Based on the results of correlation analyses, the most important single traits influencing the quality were found to be density of wool, guard hair thickness and appearance of the surface.     

Visitor effects on a zoo population of California sea lions (Zalophus californianus) and harbor seals (Phoca vitulina)

The effects of visitor presence on zoo and aquarium animals have become increasingly well studied, using measures such as behavioral responses and exhibit usage. Many taxa remain underrepresented in this literature; this is the case for marine mammals, despite widespread public concern for their welfare in managed care settings. The current study therefore used behavioral activity budgets and exhibit usage to assess the responses of California sea lions (Zalophus californianus) and harbor seals (Phoca vitulina) to visitors at the Seal Cove exhibit at Six Flags Discovery Kingdom, Vallejo CA. Data was collected via focal follow video recordings over the summer season of 2016, and analyzed using MANCOVAs, discriminant analyses, and modified Spread of Participation Indices. The sea lions showed no significant changes in behavior when visitors were present, but did show greater preference for the water bordering visitor viewing areas during these times. Two sea lions gave birth during the study period, and showed greater preference for land areas both adjacent to and out of sight of visitors when nursing compared to while pregnant. In contrast, the harbor seals showed significant behavioral changes in the presence of visitors, including increased vigilance and feeding. This was associated with increased preferential use of water areas adjacent to the visitor viewing area. Visitors were able to purchase fish to throw to the animals, which likely contributed to the differences observed. Overall, this study found little evidence for negative visitor impacts on two pinniped species in a zoo setting.     

Sex‐related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

The population of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea is in a unique position on the continental shelf edge, with vast shelf waters to the south, and deep Southern Ocean to the north. We describe sex‐related differences in the winter distribution of this population, from data collected by 20 conductivity‐temperature‐depth satellite relay data loggers deployed in February 2011 at the end of the annual molt. The regional daily speed was calculated, and a state‐space model was used to estimate behavioral states to positions along individuals’ tracks. GLMMs estimated that males and smaller individuals, diving in shallower water, traveled less far per day of deployment (males 14.6 ± 2.26 km/d, females 18.9 ± 2.42 km/d), and males were estimated to dive in shallower water (males 604 ± 382 m, females 1,875 ± 1,458 m). Males and smaller individuals were also estimated to be more resident; males spent an average 83.4% ± 7.7% of their time in a resident behavioral state, compared to females at 74.1% ± 7.1%. This evidence that male and female Weddell seals in the southern Weddell Sea are adopting different strategies has not been shown elsewhere along their circumpolar distribution.