Pup Counts Research Articles

Comparison of two bedding types on the breeding fecundity of C57BL/6J mice.

One of the favored options for generating complex transgenic laboratory mice is through in-house breeding and management strategies. One consideration in the management of these colonies is how the animals' environment may affect reproductive success. Several aspects of the microenvironment can be controlled or manipulated, including cage type, bedding, enrichment, diet, and temperature and humidity. This study sought to evaluate reproductive outcomes for C57BL/6J mice that were randomly assigned to one of two different bedding types: paper based or corncob bedding. Our hypothesis was there would be no significant difference in reproductive outcomes between the two bedding types. A total of 10 males and 10 females were paired at 45 days of age. Animals were allowed to breed for 15 consecutive weeks. Cages were checked daily for the presence of pups and a pup count was performed at 7 days of age. Weaning occurred at 20 or 21 days of age, at which time a final pup count, pup weight, and sex were recorded. All litters born and pups weaned in the 15-week timeframe were used for data analysis. Statistical analysis compared cannibalization between the two groups and the results showed no statistical difference between groups (p > 0.05). Other parameters analyzed included average litter size, average weaning weight, and number of litters per group. All pups counted at Day 7 survived to weaning age in both groups. We concluded that both bedding types produced similar success regarding breeding fecundity in C57BL/6J mice.

Effects of the 2014-2016 marine heatwave on Steller sea lions in the Gulf of Alaska and implications for top-down forcing

Marine heatwaves can have rapid and wide-reaching biological and economic impacts. We explored the effects of a recent severe marine heatwave on Steller sea lions in the Gulf of Alaska and Southeast Alaska using biennial counts of pups and non-pups from aerial surveys of terrestrial sites between 2013 and 2019. We combined count data with a bioenergetic model to explore the potential effects of Steller sea lion responses to the heatwave on prey populations. Pup production was anomalously low in the eastern and central Gulf in 2017 following the end of the heatwave in 2016, with a 33.5 and 17.4% reduction from 2015 values respectively. Based on the energetic costs of pregnancy and lactation, these reductions in pup production represent an average difference of 6121 metric tons of prey between 2015 and 2017. Non-pup counts were anomalously low in Southeast Alaska in 2017 and in the central and eastern Gulf in 2019. No effects were detected in the western Gulf, although they could have been masked by the variability in count estimates. Such changes in non-pup abundance had the potential to induce changes in predation pressure on the order of thousands to tens of thousands of metric tons of prey, even when responses were assumed to persist for a relatively short time (1 yr or less). In addition to these short-term effects, declining counts of non-pups from the eastern Gulf and Southeast Alaska occurred following the 2014-2016 heatwave, suggesting more lasting effects on Steller sea lion populations and top-down forcing from these regions.

Merging integrated population models and individual-based models to project population dynamics of recolonizing species

Recolonizing species exhibit unique population dynamics, namely dispersal to and colonization of new areas, that have important implications for management. A resulting challenge is how to simultaneously model demographic and movement processes so that recolonizing species can be accurately projected over time and space. We introduce a framework for spatially explicit projection modeling that harnesses the rigorous parameter estimation made possible by an integrated population model (IPM) and the flexible movement modeling made possible by an individual-based model (IBM). Our framework has two components: [1] a Bayesian IPM-driven age- and state-structured population model that governs the population state process and estimation of demographic rates, and [2] an IBM-driven spatial model that allows for the projection of dispersal and habitat colonization. We applied this model framework to estimate current and project future dynamics of gray wolves (Canis lupus) in Washington State, USA. We used data from 74 telemetered wolves and yearly pup and pack counts to parameterize the model, and then projected statewide dynamics over 50 years. Mean population growth was 1.29 (95 % Bayesian Credible Interval = 1.26–1.33) during initial recolonization from 2009 to 2020 and decreased to 1.02 (95 % Prediction Interval = 0.98–1.04) in the projection period (2021–2070). Our results suggest that gray wolves have an ~100 % probability of colonizing the last of Washington State's three specified recovery regions by 2030, regardless of alternative assumptions about how dispersing wolves select new territories. Our spatially explicit projection model can be used to project the dynamics of any species for which spatial spread is an important driver of population dynamics.

Decline of one of the southernmost northern elephant seal (Mirounga angustirostris) colonies and its relationship with a warm sea environment

Over several decades, air temperature and sea surface temperature (SST) have increased in the northeastern Pacific, as has the frequency of large-scale warm anomalies in SST. The objective of this study was to evaluate the impact of these warm anomalies on the production of northern elephant seal (Mirounga angustirostris; NES) pups from the colony of the San Benito Archipelago, located in the central-western region of the Baja California Peninsula. Pup and adult female counts from the 2002 to 2019 breeding seasons were compiled to determine the trend in the abundance of the colony and its current state. In addition, birth rate variations during the study period were assessed. Likewise, the presence of warm anomaly events in the SST in the potential foraging area of adult females (PFA) was analyzed. The San Benito colony decreased at an average annual rate of 3.6% from 2002 to 2019, with an estimated abundance of 4,723 individuals (95% CI: 3,821–5,615) in 2019. However, the birth rate remained constant (mean 0.68 ± 0.08), even though several warm anomaly events associated with El Niño and The Blob phenomena were detected in the PFA. Our results suggest that large-scale warm anomalies in the SST do not severely impact NES pup production, thus the decline of the San Benito colony since the late 1900s could be due to other environmental factors, such as the increase in air temperature associated with climate change.

Phenology of harbor seal pupping and the influence of weather on pup counts, investigated by UAV

AbstractSurveys of harbor seals to assess pup production in Denmark are conducted at the assumed breeding season peak between 9 and 15 hr at winds <10 m/s, with no precipitation at least 6 hr before observations and at low tide in areas with a significant tidal range. Harbor seal pups can swim immediately after birth, so the fraction available for counting likely varies according to conditions. In the Limfjord, a separate harbor seal population is living in a large inlet in northern Denmark where >95% of pups are born at two haul‐out sites situated 4 km apart. Drone surveys of these two haul‐outs were conducted throughout the breeding seasons during 2017–2019. The effects of weather conditions and timing of surveys on counts were analyzed by generalized additive mixed models. The best‐performing model included date and wind speed. Pup counts grew from the onset of the observation period and were predicted to peak on June 22. Wind speed had a linear relationship with pup counts and > 50% more pups were counted at 5 m/s than at 1 m/s. To achieve representative pup counts careful consideration of survey conditions and possibly correction for these effects are necessary.

Characteristics of ringed seal Pusa hispida (‘natchiq’) denning habitat in Kotzebue Sound, Alaska, during a year of limited sea ice and snow

Sea ice and snow are essential to Arctic ecosystems, playing key roles in the lives of Arctic marine mammals and the Indigenous Peoples who rely on them. Ringed seals Pusa hispida (‘natchiq’ in Iñupiaq) use snow-covered dens on sea ice for pupping, but quantitative information on denning habitat requirements is limited, and it is unknown how changes in snow depth and sea-ice extent will impact ringed seals. Here, an Indigenous Elder Advisory Council and a multidisciplinary group of scientists used knowledge co-production to quantify fine-scale ringed seal habitat selection patterns in Kotzebue Sound, Alaska (USA), during a year of unprecedentedly limited snow and sea-ice availability. Together, we conducted unoccupied aerial vehicle-based surveys during spring 2019 and related seal counts to survey date, bathymetry, and novel proxies for snow depth and surface roughness that we derived from Landsat 8 surface reflectance and validated with on-ice measurements. Generalized additive models showed that counts of seal groups (all age classes) and pups were associated with later survey dates, deeper water, and habitat with bright Landsat 8 pixel values and intermediate pixel variability, which in turn were correlated with deep snow and surface roughness. We observed shallow snow depths, early sea-ice breakup, and high seal densities consistent with the extreme lack of ice available in 2019. Indigenous Knowledge, intentionally woven with scientific data, provided novel and more nuanced understandings of snow and sea-ice conditions for seals. Our results may give a glimpse at future ringed seal habitat and selection in a warming Arctic.

Variation in adult and pup wolf diets at natal den sites is influenced by forest composition and configuration.

Although wolves are wide-ranging generalist carnivores throughout their life cycle, during the pup-rearing season wolf activity is focused on natal den sites where pup survival depends upon pack members provisioning food. Because prey availability is influenced by habitat quality within the home range, we investigated the relative importance of prey species for adults and pups and further examined the relationship between habitat characteristics, wolf diet, and litter size on Prince of Wales Island (POW) in Southeast Alaska. During 2012-2020, we detected 13 active den sites within the home ranges of nine wolf packs. We estimated minimum pup counts using motion-detecting cameras and individual genotypes from noninvasive samples (hair: n=322; scat: n=227) and quantified wolf diet composition using fecal DNA metabarcoding (n=538). We assessed habitat composition, configuration, and connectivity within denning and annual home ranges estimated using wolf GPS-collar data. Contrary to expectations, wolves had a more constricted diet during denning season (April 15-July 31), and within this season pups had a narrower dietary niche (species richness [S]=4) focused more on deer (relative frequency of occurrence [O/I]=0.924) than adults (S=15; deer O/I=0.591). Litter size had a positive relationship with the relative frequency of deer in a wolf pack's diet. Wolf consumption of deer was positively associated with the proportion of young-growth forest (≤25 years old) within denning and annual home ranges. High levels of vegetation patch interspersion, and the density of closed logging roads were also important predictors, suggesting these habitat qualities were influential for increasing the availability of deer to wolves. Our results contrast with previous research indicating wolf pup diets included more alternate prey (i.e., beaver) than adults and emphasize the importance of deer to wolf viability on POW, especially during denning season.

Using ‘pup multipliers’ to estimate demographic parameters of Mediterranean monk seals in the eastern Mediterranean Sea

A thorough understanding of population demographics is important in planning and evaluating conservation actions. At the same time, it is also essential that conservation management strives to minimize uncertainty in decision making in order to avoid management errors, which in the case of endangered species might affect their persistence. Mediterranean monk seals are endangered and have been notoriously difficult to count, especially in the eastern Mediterranean Sea, where abundance estimates have relied mainly on expert judgement. To address this problem, a new approach to estimating the species’ demographics using ‘pup multipliers’ is introduced. Adopting a conservative and a more optimistic approach and following a review of the available species- and taxa-specific data, the following multipliers were proposed: 2.5-3.5 for estimating the number of mature individuals, and 4.5-6.0 for estimating the total number of individuals. These multipliers were then used to calculate, in a formal way, the population demographics of the Mediterranean monk seal in the eastern Mediterranean Sea and globally. In their current form, the pup multipliers proposed present a number of strengths, but also several caveats, limitations and/or points of concern and should therefore not be considered a panacea in the conservation of the species, but merely the starting point of efforts for further development. These efforts should ultimately aim at developing a population-specific pup multiplier for the Mediterranean monk seal that is based on a common monitoring approach between various countries and includes the collection of newborn pup count data from across the species’ range in the eastern Mediterranean Sea.

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.

State of the California Current Ecosystem in 2021: Winter is coming?

In late 2020, models predicted that a strong La Niña would take place for the first time since 2013, and we assessed whether physical and biological indicators in 2021 were similar to past La Niñas in the California Current Ecosystem (CCE). The Pacific Decadal Oscillation and Oceanic Niño Index indeed remained negative throughout 2021; the North Pacific Gyre Oscillation Index, however, remained strongly negative. The seventh largest marine heatwave on record was unexpectedly present from April to the end of 2021; however, similar to past La Niñas, this mass of warm water mostly remained seaward of the continental shelf. As expected from past La Niñas, upwelling and chlorophyll were mostly high and sea surface temperature was low throughout the CCE; however, values were close to average south of Point Conception. Similar to past La Niñas, abundances of lipid-rich, northern copepods off Oregon increased. In northern California, unlike past La Niñas, the body size of North Pacific krill (Euphausia pacifica) was close to average. Predictably, overall krill abundance was above average in far northern California but, unexpectedly, below average south of Cape Mendocino. Off Oregon, similar to past La Niñas, larval abundances of three of six coastal species rose, while five of six southern/offshore taxa decreased in 2021. Off California, as expected based on 2020, Northern Anchovy (Engraulis mordax) were very abundant, while Pacific Sardine (Sardinops sagax) were low. Similar to past La Niñas, market squid (Doryteuthis opalescens) and young of the year (YOY) Pacific Hake (Merluccius pacificus), YOY sanddabs (Citharichthys spp.), and YOY rockfishes (Sebastes spp.) increased. Southern mesopelagic (e.g., Panama lightfish Vinciguerria lucetia, Mexican lampfish Triphoturus mexicanus) larvae decreased as expected but were still well above average, while northern mesopelagic (e.g., northern lampfish Stenobrachius leucopsarus) larvae increased but were still below average. In line with predictions, most monitored bird species had above-average reproduction in Oregon and California. California sea lion (Zalophus californianus) pup count, growth, and weight were high given the abundant Anchovy forage. The CCE entered an enduring La Niña in 2021, and assessing the responses of various ecosystem components helped articulate aspects of the system that are well understood and those that need further study.

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.

The effect of Propofol versus Dexmedetomidine as anesthetic agents for oocyte pick-up on in vitro fertilization (IVF) outcomes

This study aimed to evaluate the effects of propofol and dexmedetomidine over different timescales on the IVF outcomes for transvaginal oocyte retrieval (TVOR). Twenty-four rats included in the study were divided into two main groups and three subgroups were subjected to the ovulation induction process. Group 1 was administered propofol (100 mg/kg i.v.) and group 2 were administered dexmedetomidine (25 µg/kg i.p.) The oviduct collection procedure was completed within 15 min for subgroup Pro15min, Dex15min (n = 4), within 16 to 30 min for subgroup Pro30min, Dex30min (n = 4) and within 31 to 60 min for subgroup Pro60min, Dex60min (n = 4) after euthanasia. The total number of oocytes was counted. After in vitro fertilization, the number and quality of embryos were evaluated. The number of pups born were evaluated after embryo transfer. The embryo number, quality and pup count decreased as the administration time for propofol increased (p < 0.05). No statistically significant difference was found between the dexmedetomidine subgroups for embryo number, quality and pup count(p > 0.05). As the exposure time to propofol increased, the number and quality of embryos obtained, and the pup count, decreased. The use of dexmedetomidine had no negative impacts on the number of embryos, their quality or the number of pups.

Pup numbers, estimated population size, and monitoring of New Zealand fur seals in Doubtful/Pateā, Dusky and Breaksea Sounds, and Chalky Inlet, Fiordland, New Zealand 2021

ABSTRACT New Zealand fur seals (Arctocephalus forsteri) are expanding in numbers and distribution throughout New Zealand. The exception is the West Coast of the South Island, where there is documented decline due to decades of mortalities related to fishery. There are fur seal colonies south of these West Coast colonies, in Fiordland, which have never been accurately documented or monitored. Even for those that are documented, there are few records of pup numbers and no population estimates. Here, pups at colonies from Doubtful/Pateā, Dusky, and Breaksea Sound, and Chalky Inlet were observed, and their numbers either counted directly or estimated using mark-recapture methods in February 2021. From these pup counts a coarse minimum population estimate of between 14–24 thousand fur seals is calculated for lower Fiordland. The pup counts and population estimates indicated the fur seal numbers are higher than previously recorded from estimates of walk through, boat or helicopter observations. During onshore surveys and from anecdotal evidence, it was noted that fur seals were rearing pups in forested areas. This paper outlines suggestions for the future monitoring of these colonies given, location, diverse geology and the difficulty of monitoring colonies on exposed west coast areas of New Zealand’s Fiordland.

Report of the NAMMCO-ICES Workshop on Seal Modelling (WKSEALS 2020)

To support sustainable management of apex predator populations, it is important to estimate population size and understand the drivers of population trends to anticipate the consequences of human decisions. Robust population models are needed, which must be based on realistic biological principles and validated with the best available data. A team of international experts reviewed age-structured models of North Atlantic pinniped populations, including Grey seal (Halichoerus grypus), Harp seal (Pagophilus groenlandicus), and Hooded seal (Cystophora cristata). Statistical methods used to fit such models to data were compared and contrasted. Differences in biological assumptions and model equations were driven by the data available from separate studies, including observation methodology and pre-processing. Counts of pups during the breeding season were used in all models, with additional counts of adults and juveniles available in some. The regularity and frequency of data collection, including survey counts and vital rate estimates, varied. Important differences between the models concerned the nature and causes of variation in vital rates (age-dependent survival and fecundity). Parameterisation of age at maturity was detailed and time-dependent in some models and simplified in others. Methods for estimation of model parameters were reviewed and compared. They included Bayesian and maximum likelihood (ML) approaches, implemented via bespoke coding in C, C++, TMB or JAGS. Comparative model runs suggested that as expected, ML-based implementations were rapid and computationally efficient, while Bayesian approaches, which used MCMC or sequential importance sampling, required longer for inference. For grey seal populations in the Netherlands, where preliminary ML-based TMB results were compared with the outputs of a Bayesian JAGS implementation, some differences in parameter estimates were apparent. For these seal populations, further investigations are recommended to explore differences that might result from the modelling framework and model-fitting methodology, and their importance for inference and management advice. The group recommended building on the success of this workshop via continued collaboration with ICES and NAMMCO assessment groups, as well as other experts in the marine mammal modelling community. Specifically, for Northeast Atlantic harp and hooded seal populations, the workshop represents the initial step towards a full ICES benchmark process aimed at revising and evaluating new assessment models.

Modeling ringed seal Pusa hispida habitat and lair emergence timing in the eastern Bering and Chukchi Seas

Ringed seals Pusa hispida are reliant on snow and sea ice for denning, and a better understanding of ringed seal habitat selection and timing of emergence from snow dens (also called lairs) is needed to quantify and predict effects of climate change in the Arctic. We used generalized additive models to assess relationships between ringed seal counts, from spring aerial surveys in the Bering Sea (2012 and 2013) and Chukchi Sea (2016), and spatiotemporal covariates including survey date, remotely sensed snow and sea-ice values, and short-term weather data. We produced separate models for total ringed seal counts and for pup counts within each region. Our models showed that in both areas, total ringed seal counts increased over the course of the spring, especially after 15 May, indicating emergence from lairs and/or the onset of basking behavior. For the more northerly Chukchi Sea, we found a substantial unimodal effect of snow melt progression and a positive effect of snow depth on total ringed seal counts. In contrast, Bering Sea total ringed seal counts and pup counts in both regions were affected much more strongly by date than by habitat variables. Overall, our findings demonstrate that snow depth and melt play an important role in the timing of ringed seal den emergence, particularly in the Chukchi Sea, and suggest that ringed seal denning may be affected by continued shifts in melt and snow depth associated with climate change.

Risk exposure trade-offs in the ontogeny of sexual segregation in Antarctic fur seal pups.

Sexual segregation has important ecological implications, but its initial development in early life stages is poorly understood. We investigated the roles of size dimorphism, social behavior, and predation risk on the ontogeny of sexual segregation in Antarctic fur seal, Arctocephalus gazella, pups at South Georgia. Beaches and water provide opportunities for pup social interaction and learning (through play and swimming) but increased risk of injury and death (from other seals, predatory birds, and harsh weather), whereas tussock grass provides shelter from these risks but less developmental opportunities. One hundred pups were sexed and weighed, 50 on the beach and 50 in tussock grass, in January, February, and March annually from 1989 to 2018. Additionally, 19 male and 16 female pups were GPS-tracked during lactation from December 2012. Analysis of pup counts and habitat use of GPS-tracked pups suggested that females had a slightly higher association with tussock grass habitats and males with beach habitats. GPS-tracked pups traveled progressively further at sea as they developed, and males traveled further than females toward the end of lactation. These sex differences may reflect contrasting drivers of pup behavior: males being more risk prone to gain social skills and lean muscle mass and females being more risk averse to improve chances of survival, ultimately driven by their different reproductive roles. We conclude that sex differences in habitat use can develop in a highly polygynous species prior to the onset of major sexual size dimorphism, which hints that these sex differences will increasingly diverge in later life.

Rates of increase in gray seal (Halichoerus grypus atlantica) pupping at recolonized sites in the United States, 1988-2019.

Gray seals were historically distributed along the northeastern coast of the United States, but bounties and lack of protection reduced numbers and they were rarely observed for most of the 20th century. Once protections were enacted, the population started to rebound. Here, we describe the recolonization and recovery of gray seals in the United States, focusing on the re-establishment of pupping sites. We fit individual generalized linear models to various time series (1988–2019) to estimate rates of increase in observed pup counts at four of the more data-rich sites. Annual rate of increase at individual sites ranged from −0.2% (95% CI: −2.3–1.9%) to 26.3% (95% CI: 21.6–31.4%). The increase in sites and number of pups born in the United States is driven by population growth and immigration from Canadian colonies and is part of a larger recovery of the Northwest Atlantic population. Wildlife protection, a healthy source population, habitat availability, and species traits that allow for dispersal and high productivity were all important factors in this recovery.

Re‐evaluating the population size of South American fur seals and conservation implications

Abstract South American fur seals (Arctocephalus australis) are widely distributed, yet surprisingly little is known about their ecology. In particular, population data are sparse and outdated for many breeding locations, including the Falkland Islands. Data deficiency impedes the development of coherent conservation and management strategies. To address knowledge gaps, for the first time since 1965 an archipelago‐wide census of South American fur seals breeding at the Falkland Islands was undertaken, which provided the first pup abundance estimate since 1926 – data that are critical for assessing population trends. In total, 36,425 South American fur seal pups were counted at the Falkland Islands in 2018, a greater than four‐fold increase since the last census, and far greater than the 7,990 pups counted in Uruguay, which was presumed to be the largest South American fur seal population in the world. Hence, based on pup abundance, the Falkland Islands is presently the largest population of South American fur seals, even when considering a correction factor of 3.9 that was applied to pup counts in Uruguay, which yielded an estimated 31,160 pups. The results redefine South American fur seal abundance, the contribution of breeding locations (Falkland Islands, Uruguay, Argentina, Chile) and the distribution of breeding colonies at the Falkland Islands, which has far reaching implications for conservation and management. In particular, the present study has effectively doubled the Atlantic population size of the species, which is now estimated to comprise about 76,000 pups, of which the Falkland Islands accounts for 48% and Uruguay 41%. Accordingly, changes in the number of South American fur seals breeding at the Falkland Islands will influence the global population trends and conservation status of the species. Monitoring South American fur seals breeding at the Falkland Islands is therefore crucial to understand the impacts of anthropogenic pressures, such as fisheries, and to inform management and conservation policy. The results provide a baseline from which to measure changes in abundance.

Monitoring long‐term changes in UK grey seal pup production

Abstract The population size of many species, particularly those in the aquatic environment, cannot be censused directly. Counts, during the breeding season, of one component of the population (e.g. breeding females) are often used as an index to allow investigation of trends. In species, such as grey seals (Halichoerus grypus), for which births are not tightly synchronous, single counts of pups represent an unknown proportion of the total number of pups born (pup production), and thus of breeding females (i.e. each pup born represents a breeding female). Grey seals pup at large colonies around the coast of the UK. Information on their populations is required under national and international legislation. In the UK, pup production has been monitored at some colonies since 1956. Currently, large colonies (~90% of UK pup production) are monitored either using ground (~10%; annually) or aerial surveys (~80%; annually until 2010, and thereafter biennially). Here, the model used to estimate pup production at aerially surveyed colonies from 1987 to 2010 is described; structured pup counts from multiple surveys are combined with knowledge of life‐history parameters to model birth curves. The resulting trends in pup production up to 2010 (aerially surveyed colonies) and 2016 (ground surveyed colonies) are examined. In 2010, over 45,000 pups were estimated to be born in the UK. Pup production appeared to have reached an asymptote in the Inner Hebrides, Outer Hebrides and Orkney, whereas it is still increasing exponentially in the North Sea. Although density‐dependent processes acting at sea are likely to be responsible for these regional trends, we suggest that the substantial variation in trends within regions are likely caused by processes acting at the colony level. Some long‐established colonies, including Special Areas of Conservation, are exhibiting decreasing trends. Special Areas of Conservation often serve as de facto monitoring sites and are the focus of management efforts. The observed temporal and spatial variability in patterns of colony growth rates highlight the potential risks of using such sites to develop wider management policies.

Population status of the Guadalupe fur seal (Arctocephalus townsendi)

The Guadalupe fur seal (GFS, Arctocephalus townsendi) was distributed on the islands of Baja California, Mexico, and southern California, United States. The species was intensively hunted during the 19th century, and in the late 1920s it was thought that it was extinct, but in 1954, a few animals were located on Isla Guadalupe, Baja California. Since the current status of the GFS population is unknown, we used counts of pups collected between 1984 and 2013 from Isla Guadalupe, which is still the only place where the species reproduces, and used Bayesian inference to assess both the population trend and abundance. The GFS population increased from 1984 to 2013 at an average annual growth rate of 5.9% (range 4.1–7.7%), and for 2013 the abundance was estimated between 34,000 and 44,000 individuals. The current abundance of the GFS represents about one-fifth of the estimated historical population size, and although the population has continued to increase, the species has not expanded its breeding range, which potentially affects its recovery.