Fur Seal Pups Research Articles

Maternal care strategies differentially optimize the health and immunity of male and female South American fur seal pups

Maternal care strategies differentially optimize the health and immunity of male and female South American fur seal pups

Abduction and sexual coercion of Guadalupe fur seal pups

Abduction and sexual coercion of Guadalupe fur seal pups

Weather, climate, and entry into migration of northern fur seal pups

Weather, climate, and entry into migration of northern fur seal pups

How Cape fur seal mums and pups reunite by ear

How Cape fur seal mums and pups reunite by ear

Little evidence of inbreeding depression for birth mass, survival and growth in Antarctic fur seal pups

Inbreeding depression, the loss of offspring fitness due to consanguineous mating, is generally detrimental for individual performance and population viability. We investigated inbreeding effects in a declining population of Antarctic fur seals (Arctocephalus gazella) at Bird Island, South Georgia. Here, localised warming has reduced the availability of the seal’s staple diet, Antarctic krill, leading to a temporal increase in the strength of selection against inbred offspring, which are increasingly failing to recruit into the adult breeding population. However, it remains unclear whether selection operates before or after nutritional independence at weaning. We therefore used microsatellite data from 885 pups and their mothers, and SNP array data from 98 mother–offspring pairs, to quantify the effects of individual and maternal inbreeding on three important neonatal fitness traits: birth mass, survival and growth. We did not find any clear or consistent effects of offspring or maternal inbreeding on any of these traits. This suggests that selection filters inbred individuals out of the population as juveniles during the time window between weaning and recruitment. Our study brings into focus a poorly understood life-history stage and emphasises the importance of understanding the ecology and threats facing juvenile pinnipeds.

Estimating whisker growth rates and foraging profiles for northern fur seal pups and adult females using stable isotope analysis

Changing ratios of stable carbon ( δ13C) and nitrogen ( δ15N) isotopes in consumer tissues reflect foraging patterns over time and can be used to inform studies on historically vulnerable populations. Northern fur seals (NFS; Callorhinus ursinus) at San Miguel Island (SMI), California, have been severely impacted by climate events such as El Niño and remain susceptible to future environmental disturbances, necessitating the need to further understand their foraging ecology. We analyzed sequential δ13C and δ15N values along single NFS whiskers sampled from five pups and five unrelated post-parturient females at SMI and reconstructed temporally aligned stable isotope profiles for each whisker. Pup profiles consistently showed increases in postnatal δ13C and δ15N values that likely stem from pup consumption of maternal milk and changes in maternal foraging locations after parturition. Adult female profiles indicated predominantly heterogeneous foraging strategies and minimal foraging outside the Southern California Bight. These findings provide initial characterizations of longitudinal, stable isotope-derived foraging data for NFS from SMI and offer insight into the inference of otariid foraging ecology with sequential δ13C and δ15N values.

Vulnerability to fluctuations in prey and predation landscape in a central place foraging marine predator

IntroductionHuman-induced environmental change is driving a global redistribution of biodiversity, resulting in shifting prey and predation landscapes. These shifting landscapes can lead to changes in behavior, health, and vital rates, with potential implications for population dynamics.MethodsIn the present study, a state-dependent life-history theory model was developed to investigate the individual- and population-level responses of Australian fur seals (Arctocephalus pusillus doriferus) to changes in prey availability and at-sea mortality risk.ResultsRates of pregnancy, pup nursing, and abortion were unaffected by prey availability in the simulated population. Likewise, on-land and at-sea durations were largely unaffected by prey availability, with more pronounced affects for nonreproductive and pregnant females than for lactating females. There was a strong influence of prey availability on the proportion of females that were concurrently pregnant and lactating, largely due to an increase in pup abandonments under low prey availability scenarios. This effect on pup abandonments also had flow on effects for pup recruitment. Increasing at-sea mortality risk resulted in greater offspring losses due to maternal death. The combined impact of prey availability and at-sea mortality risk on the number of simulated female offspring reaching sexual maturity was substantial.DiscussionConsequently, our results suggest high vulnerability of the Australian fur seal population to shifting prey and predation landscapes. These results indicate a need for continued monitoring of Australian fur seal pup production and population dynamics in the face of rapid environmental change.

Isochrony in barks of Cape fur seal (Arctocephalus pusillus pusillus) pups and adults.

Animal vocal communication often relies on call sequences. The temporal patterns of such sequences can be adjusted to other callers, follow complex rhythmic structures or exhibit a metronome-like pattern (i.e., isochronous). How regular are the temporal patterns in animal signals, and what influences their precision? If present, are rhythms already there early in ontogeny? Here, we describe an exploratory study of Cape fur seal (Arctocephalus pusillus pusillus) barks-a vocalisation type produced across many pinniped species in rhythmic, percussive bouts. This study is the first quantitative description of barking in Cape fur seal pups. We analysed the rhythmic structures of spontaneous barking bouts of pups and adult females from the breeding colony in Cape Cross, Namibia. Barks of adult females exhibited isochrony, that is they were produced at fairly regular points in time. Instead, intervals between pup barks were more variable, that is skipping a bark in the isochronous series occasionally. In both age classes, beat precision, that is how well the barks followed a perfect template, was worse when barking at higher rates. Differences could be explained by physiological factors, such as respiration or arousal. Whether, and how, isochrony develops in this species remains an open question. This study provides evidence towards a rhythmic production of barks in Cape fur seal pups and lays the groundwork for future studies to investigate the development of rhythm using multidimensional metrics.

Recommendations for the development of a carnivore viewing site at a colony of Cape fur seals (Arctocephalus pusillus pusillus) in southern Namibia

ABSTRACT This study examined the daily and monthly activity patterns of brown hyenas (Hyaena brunnea) and black-backed jackals (Canis mesomelas) at a Cape fur seal colony in southern Namibia, to provide recommendations for developing a sustainable wildlife viewing site. Observations conducted between November 2020 and October 2022 showed that the carnivores were most active between May and October, with jackals showing peak activity around sunrise and sunset, and brown hyenas mostly visiting around midday. The animals were more active during cloudy and cool weather. With the diurnal activity of carnivores and their predation behaviour on Cape fur seal (Arctocephalus pusillus pusillus) pups, the area has high ecotourism potential. Brown hyenas, however, are sensitive to human disturbance, such as moving vehicles and unknown sounds and smells. Therefore, limiting the number of visitors and creating a fixed viewpoint is recommended to minimise disturbance. This study provides valuable input on how ecotourism activities could be developed at a seal colony without compromising the sensitive wildlife there.

First record of ocular albinism in sub-Antarctic fur seal (Arctocephalus tropicalis) pups on Marion Island

We report on an occurrence of ocular albinism in sub-Antarctic fur seal (Arctocephalus tropicalis) pups born on Marion Island, Prince Edward Archipelago. While previous observations have documented pups with atypical lanugo pelage colorations, this is the first case involving hypopigmentation of both fur and other tissues, including the eyes and nails. During the austral summer of 2021/22, we encountered four sub-Antarctic fur seal pups displaying this anomalous pigmentation. These anomalous individuals were found along two beaches on the island’s western side and one beach on the eastern side during an island-wide fur seal census. Although the characteristics observed strongly suggest ocular albinism, confirmation would be necessary through genetic analyses. The absence of melanin in mammalian eyes is known to compromise visual acuity, which may likely result in reduced survival beyond the weaning period, explaining the paucity of such adults in this well-observed population.

Geographical variation in Cape fur seals' in‐air vocalizations across Southern Africa (Namibia and South Africa)

AbstractThe use of acoustic signals to communicate is widespread among marine mammals and vocalizations are involved in all their social interactions. Due to many factors, acoustic features of a species' vocalizations may differ among populations. The present study investigated both micro‐ and macro‐geographical variation in the vocalizations of Cape fur seal females, males, and pups. Acoustic measurements were performed on calls recorded at four South African and two Namibian sites (maximum range ~ 1,000 km). Comparisons among close sites in South Africa revealed no micro‐geographical variation (maximum range ~130 km) in females' and pups' vocalizations. Barks of subadult males had different features among sites, which may be explained mostly by the context of call production. At the macro‐geographical scale (South Africa vs. Namibia), all call types varied significantly among sites. Several extrinsic and intrinsic factors were suggested to drive such differences. For females' and pups' calls, differences might be explained by environmental factors, whereas for males' barks, behavioral differences are the most likely explanation for acoustic differences (breeding vs. resting sites). Such investigations help understand how acoustic communication in marine mammals is shaped by ecological drivers.

Reproductive investment in female fur seals in relation with age of puberty

Purpose: To find out the main parameters of the life cycle and the reproductive contribution of females depending on the age of their puberty.Method: Analysis of metal tagging in fur seal pups and tag return obtained by reading tags on live fur seals using optical instruments. Reading marks was carried out in 1982-2014 during the harem period on the Central site of the Northern rookery (Bering Island).Novelty: For the first time, data have been obtained on the reproductive contribution of female fur seals during the life cycle in relation to their age of puberty.Results: The birth of puppies in early maturing (at 2-3 years old) females is shifted to an earlier age, their life cycle is shorter, natural loss after the first fertilization is higher, they miss more breeding seasons during the life cycle. During the life cycle, early maturing females give birth to about 40% of the total number of puppies born by tagged females, and most of them (31%) are under the age of 8 years. Medium maturing (at 4-5 years old) females give birth to almost the same number of puppies (39.7%), however, the proportion of puppies born in these females is distributed more evenly over the life cycle. In late-maturing (at 6-7 years old) females and females entering the rookery at the age of 8+ years, the reproductive contribution is lower - they give birth to 13.4% and 6.3% of puppies, respectively, and the age at which puppies are born is higher - mostly 11 years and older.

Is regional variability in environmental conditions driving differences in the early body condition of endemic Australian fur seal pups?

Context Good body condition in juvenile marine mammals is crucial for survival and, therefore, population demography. Australian fur seals, endemic to Australia, recently established a breeding colony at the southern edge of their range, at The Needles, a small group of islands in south-west Tasmania (43.6614°S) and a significant distance from their core breeding range in Bass Strait. Aims We aimed to compare pup body condition at two breeding colonies, distinct in time since establishment and latitude. Specific aims were to: (1) establish the timing of peak pupping, to compare condition of known-age pups, and determine a baseline at The Needles; (2) investigate pup body condition over time at an established colony; and (3) gain insight into the effects of environmental conditions on pup body condition. Methods We conducted a colony comparison of pup body condition using condition indices at The Needles and an established breeding colony in Bass Strait, Tenth Island, for the 2019/20 and 2020/21 breeding seasons. Pup body condition was quantified at Tenth Island over 18 years (2003–2020) using a long-term morphometric dataset. To establish breeding phenology at these two colonies, we determined peak pupping date for the 2019/20 breeding season using daily pup counts. We assessed the effect of environmental parameters on body condition for the long-term dataset. Key results Pups from The Needles displayed significantly higher body condition than those from Tenth Island, despite similar peak pupping date. Breeding phenology was consistent with published timing for Australian fur seals. Pup body condition at Tenth Island over the 2-year colony comparison was comparable to the historical average. Environmental drivers that affect maternal foraging efficiency are linked to pup body condition. Conclusions Higher pup body condition at The Needles is likely underpinned by better foraging conditions resulting in increased pup provisioning levels. Our results indicate that south-west Tasmania is a region of foraging and emerging breeding importance for Australian fur seals. Implications Future research to monitor pup body condition, maternal foraging behaviour and ecosystem productivity at The Needles will help to provide greater understanding of likely population trajectories at this southernmost breeding site for Australian fur seals.

Implications of Escherichia coli community diversity in free-ranging Australian pinniped pups.

Escherichia coli is a widely studied bacterium, commonly used as an indicator of faecal contamination. Investigations into the structure and diversity of E. coli in free-ranging wildlife species has been limited. The objective of this study was to characterise intra-individual and inter-species E. coli phylotype and B2 sub-type diversity in free-ranging Australian pinniped pups, to determine whether a single E. coli colony is representative of the phylotype and B2 sub-type diversity in these hosts. Faecal samples were collected from free-ranging Australian fur seal (Arctocephalus pusillus doriferus), Australian sea lion (Neophoca cinerea) and long-nosed fur seal (Arctocephalus forsteri) pups from three breeding colonies between 2018 and 2021. Faecal swabs from thirty randomly selected pups (n=10 from each species) were cultured and ten E. coli colonies were selected from each culture based on morphology and separation between colonies on agar plates. Molecular screening techniques were utilised to assign isolates to phylotypes and B2 sub-types. There was no significant difference (p>0.05) in either intra-individual or inter-species E. coli phylotype and B2 sub-type diversity. The B2 phylotype was the most dominant, with 78% of isolates (n=234) assigned to this phylotype. Host factors (species, weight [kg] and standard length [cm]) did not significantly affect phylotype diversity. The absence of intra-individual and inter-species differences in E. coli diversity at a phylotype level suggests that a single E. coli colony could be used as an indicator of overall diversity of E. coli at a phylotype level in A. p. doriferus, N. cinerea and A. forsteri pups. These findings can be used to simplify and improve the efficiency of sampling protocols for ongoing monitoring of human-associated E. coli phylotypes in free-ranging pinniped populations.

Temporal patterns in Cape fur seal (Arctocephalus pusillus pusillus) mother and pup attraction calls

Vocal recognition is widespread in the animal kingdom, and a necessary tool for offspring survival in some groups. Temporal patterns of animal vocalisations can facilitate communication and convey information such as identity, emotional state, or motivation of the caller. While pinniped (i.e., walrus, eared and true seals) vocalisations are generally well studied, and captive pinnipeds show strong timing abilities, little is known about the temporal structure of their calls in the wild. Here, we followed Cape fur seals (Arctocephalus pusillus pusillus) during spontaneous search efforts at the Cape Cross Seal Reserve in Namibia. To investigate the temporal and rhythmic patterning of Cape fur seal attraction calls, we analysed call bouts of 80 mothers and 148 pups. We assessed the relative vocal efforts undertaken by mothers and pups by calculating calling rates, inter-call intervals (periods of silence between vocalisations), and the total time spent calling per bout. To explore the rhythmic structure of the calls, we visualised their temporal patterns by plotting the calling events and frequency histograms of the inter-onset-intervals between each two consecutive vocalisations in a bout. A normalized Pairwise Variability Index was calculated for each individual to investigate underlying patterns and compared between mothers and pups. Pups produced more calls per search, vocalised at higher rates, and took shorter breaks between consecutive vocalisations than females. Even though female vocalisations were much longer, there was no significant difference in the total time females and pups spent vocalising per bout. All animals vocalised at seemingly random intervals, with no distinguishable rhythmic pattern, suggesting that these do not encode identity information during mother-pup reunions. However, numerical analysis showed a potential asynchronous patterning within the age classes, possibly used in anti-masking. Our results indicate that Cape fur seal females and pups invest their energy differently during a search, and while their total calling effort is comparable, reunions seem to be driven mostly by the young.

Guadalupe fur seal pup production predicted from annual variations of sea surface temperature in the southern California Current Ecosystem

AbstractWe evaluated the effects of sea surface temperature anomalies (SSTA) in the southern California Current Ecosystem on the annual Guadalupe fur seal (Arctocephalus townsendi) pup production, a species recovering from near extinction. Pup counts from 1991 to 1993 and from 2006 to 2019 were used to estimate deviations from a long-term trend as a proxy for the population's reproductive success. We estimated interannual SSTA as a subtraction from the linear trend spanning 1991–2019 for a 778,000 km2 area, which represents the primary foraging range of adult females. The long-term increase in pup production followed an exponential curve ( ${\rm{R}}_{\rm{B}}^2 = {\rm{\ }}1$), typical of species in a recovery phase. Pup production deviations from this trend responded to SSTA during the gestation period as a cubic polynomial function ( ${\rm{R}}_{\rm{B}}^2 = {\rm{\ }}0.837$), revealing that SSTA < −0.2°C and between ∼0.6 and 1.38°C increased pup production in the subsequent breeding season, whereas normal to slightly warm (−0.17 to 0.6°C) and extreme SSTA (>1.4°C) decreased pup counts, arguably resulting from low prey availability and quality. This model allowed us to estimate pup production for years without observations, needed to understand the environmental variability influence on the recovery process of this species, and therefore constitutes a practical tool for its conservation and management.

Sustained reduction in numbers of Australian fur seal pups: Implications for future population monitoring.

Fur seal populations in the Southern Hemisphere were plundered in the late 1700s and early 1800s to provide fur for a clothing industry. Millions of seals were killed resulting in potentially major ecosystem changes across the Southern Hemisphere, the consequences of which are unknown today. Following more than a century of population suppression, partly through on-going harvesting, many of the fur seal populations started to recover in the late 1900s. Australian fur seals (Arctocephalus pusillus doriferus), one of the most geographically constrained fur seal species, followed this trend. From the 1940s to 1986, pup production remained at approximately 10,000 per year, then significant growth commenced. By 2007, live pup abundance had recovered to approximately 21,400 per year and recovery was expected to continue However, a species-wide survey in 2013 recorded a 20% decline, to approximately 16,500 live pups. It was not known if this decline was due to 2013 being a poor breeding year or a true population reduction. Here we report the results of a population-wide survey conducted in 2017 and annual monitoring at the most productive colony, Seal Rocks, Victoria that recorded a large decline in live pup abundance (-28%). Sustained lower pup numbers at Seal Rocks from annual counts between 2012–2017 (mean = 2908 ± 372 SD), as well as the population-wide estimate of 16,903 live pups in 2017, suggest that the pup numbers for the total population have remained at the lower level observed in 2013 and that the 5-yearly census results are not anomalies or representative of poor breeding seasons. Potential reasons for the decline, which did not occur range-wide but predominantly in the most populated and long-standing breeding sites, are discussed. To enhance adaptive management of this species, methods for future monitoring of the population are also presented. Australian fur seals occupy several distinct regions influenced by different currents and upwellings: range-wide pup abundance monitoring enables comparisons of ecosystem status across these regions. Forces driving change in Australian fur seal pup numbers are likely to play across other marine ecosystems, particularly in the Southern Hemisphere where most fur seals live.

Maternal offloading of arsenic and other trace elements in Peruvian fur seals

AbstractThe maternal transfer of 15 elements was examined in Peruvian fur seal (Arctocephalus australis) dam and pup paired vibrissae (whiskers), serum, and milk samples collected from 2009 to 2019. Pup vibrissae, grown in utero, represented gestational transfer, while milk represented lactational transfer. Element concentrations, except arsenic, were highest in vibrissae compared to serum and milk for both dams and pups. Mean arsenic concentrations in pup vibrissae (0.44 μg/g) and milk (0.41 μg/g) were twice as high as dam vibrissae concentrations (0.19 μg/g) and nearly ten times higher than dam (0.06 μg/g) and pup serum (0.04 μg/g) concentrations. Mean arsenic concentrations from 2011 to 2019 increased in dam vibrissae (0.026 μg/g to 0.262 μg/g) and milk (0.361 μg/g to 0.484 μg/g). Pup vibrissae had significantly higher concentrations for 11 of the 15 elements analyzed compared to dam vibrissae, suggesting that element transfer is occurring through recent exposure and remobilization of elements from dam body stores. Potentially high concentrations of aluminum, arsenic, copper, and lead in pup tissues may impact their survival and population health. The impact of regional mining activities can contribute to elevated trace elements through runoff and pose a possible threat to local marine environments.

Low heritability and high phenotypic plasticity of salivary cortisol in response to environmental heterogeneity in a wild pinniped.

Individuals are unique in how they interact with and respond to their environment. Correspondingly, unpredictable challenges or environmental stressors often produce an individualized response of the hypothalamic‐pituitary‐adrenal (HPA) axis and its downstream effector cortisol. We used a fully crossed, repeated measures design to investigate the factors shaping individual variation in baseline cortisol in Antarctic fur seal pups and their mothers. Saliva samples were collected from focal individuals at two breeding colonies, one with low and the other with high density, during two consecutive years of contrasting food availability. Mothers and pups were sampled concurrently at birth and shortly before weaning, while pups were additionally sampled every 20 days. We found that heritability was low for baseline cortisol, while within‐individual repeatability and among‐individual variability were high. A substantial proportion of the variation in baseline cortisol could be explained in pups and mothers by a combination of intrinsic and extrinsic factors including sex, weight, day, season, and colony of birth. Our findings provide detailed insights into the individualization of endocrine phenotypes and their genetic and environmental drivers in a wild pinniped. Furthermore, the strong associations between cortisol and life history traits that we report in fur seals could have important implications for understanding the population dynamics of species impacted by environmental change.

Carriage of antibiotic resistant bacteria in endangered and declining Australian pinniped pups.

The rapid emergence of antimicrobial resistance (AMR) is a major concern for wildlife and ecosystem health globally. Genetic determinants of AMR have become indicators of anthropogenic pollution due to their greater association with humans and rarer presence in environments less affected by humans. The objective of this study was to determine the distribution and frequency of the class 1 integron, a genetic determinant of AMR, in both the faecal microbiome and in Escherichia coli isolated from neonates of three pinniped species. Australian sea lion (Neophoca cinerea), Australian fur seal (Arctocephalus pusillus doriferus) and long-nosed fur seal (Arctocephalus forsteri) pups from eight breeding colonies along the Southern Australian coast were sampled between 2016–2019. DNA from faecal samples (n = 309) and from E. coli (n = 795) isolated from 884 faecal samples were analysed for class 1 integrons using PCRs targeting the conserved integrase gene (intI) and the gene cassette array. Class 1 integrons were detected in A. p. doriferus and N. cinerea pups sampled at seven of the eight breeding colonies investigated in 4.85% of faecal samples (n = 15) and 4.52% of E. coli isolates (n = 36). Integrons were not detected in any A. forsteri samples. DNA sequencing of the class 1 integron gene cassette array identified diverse genes conferring resistance to four antibiotic classes. The relationship between class 1 integron carriage and the concentration of five trace elements and heavy metals was also investigated, finding no significant association. The results of this study add to the growing evidence of the extent to which antimicrobial resistant bacteria are polluting the marine environment. As AMR determinants are frequently associated with bacterial pathogens, their occurrence suggests that these pinniped species are vulnerable to potential health risks. The implications for individual and population health as a consequence of AMR carriage is a critical component of ongoing health investigations.