Pup Production Research Articles

Sprague Dawley Female Rat Consumption of a Liquid Bait Containing Vinylcyclohexene Diepoxide and Triptolide Leads to Subfertility

Author(s): Dyer, Cheryl; Mayer, Loretta | Abstract: Worldwide, Norway rats cause significant infrastructure damage, agricultural losses, and carry zoonotic diseases. Due to rat fecundity, killing them by mechanical and/or poison does not lead to sustainable management of their populations. Our biotechnology company, SenesTech, Inc, has developed an environmentally safe oral bait taken by rats, causing them to produce fewer rat pups and take longer to deliver, without any observable adverse effects. The fertility control bait is an emulsion and contains two chemicals that cause ovarian follicle elimination; vinylcyclohexene diepoxide (VCD) targets the finite pool of primordial/primary follicles, and triptolide (T) targets growing follicles. Female Sprague Dawley rats were 33 days old when provided bait with 0.1% VCD and increasing amounts of T with unlimited chow and water for 15 days (n = 8 rats per group). The rats consumed g5% of their body weight of bait and thrived during their rapid growth phase. The day after the end of baiting, female rats were bred with untreated, proven male breeders for 21 days, then litter size and time to delivery was tracked over the next 25 days. The control group that consumed bait without active ingredients had an average litter size of 11.5 pups, treatment groups that consumed bait with T at 400, 800, or 1200 μg/kg body weight had average litter sizes respectively of 9.6, 8.3, and 3.6, and pup production per treatment group compared to control group was 83.5%, 72.2%, and 29.6% respectively with increasing T doses. Time to delivery increased significantly as T dose increased: control rats took 26.0 days versus 31.5, 38.9, and 38.2 days to delivery. We conclude our fertility control bait is a palatable liquid readily consumed by growing female rats that causes subfertility, with significantly fewer pups/litter taking 1.5 times longer to deliver. Fertility control bait effects on rat population dynamics are currently being tested in field locations.

ACCELERATED FOLLICLE DEPLETION IN VITRO AND IN VIVO IN SPRAGUE-DAWLEY RATS USING THE COMBINATION OF 4-VINYLCYCLOHEXENE DIEPOXIDE AND TRIPTOLIDE

Rodent pests cause major damage to the world's agricultural crops and food stores. Rodenticides used since World War II did not lead to sustained reduction of rodent populations, and so fertility control is becoming attractive because rats reproduce with great efficiency. Chemical acceleration of ovarian failure via oral dosing also would improve management of rat pest populations. The chemical 4-vinylcyclohexene diepoxide (VCD) is orally efficacious, causing depletion of nonregenerating primordial ovarian follicles of Sprague-Dawley rats. However, to cause rapid reduction in pups in the first breeding cycle after dosing, all stages of ovarian follicle development must be targeted. To achieve this goal, the Chinese herb triptolide was tested because it can precipitate apoptosis and deplete growing follicles. The impact of triptolide was tested in cultured postnatal day 4 Sprague-Dawley rat pup ovaries. Triptolide at 5 nM caused 100% primordial, primary, and secondary follicle depletion after 8 days of culture, compared to 38% follicle depletion caused by VCD at 30 microM. Next, a palatable rat bait was developed, containing 1% VCD with increasing concentrations of triptolide at 25, 50, and 100 microg/kg body weight. Rats ate an average 3-6% of their body weight/day over 15 feeding days. Two days after the end of baiting, rats were euthanized to conduct necropsies and collect ovaries to count all follicular stages and corpora lutea. At 50 microg triptolide/kg body weight, there was significant reduction of all follicular stages; primordial follicles were 50% lower, secondary follicles were 64% lower, antral follicles were 80% lower, and there were no corpora lutea. These results suggest that combining VCD and triptolide in an oral bait leads to significantly compromised rat ovarian function and reduced ovulations, and is likely to reduce pup production.

The status of grey seals in Britain

Grey seal pup production in Scotland was estimated through annual aerial surveys of the main grey seal breeding colonies. Between 3 and 7 counts of pups were obtained for each colony at intervals through the course of the breeding season. Pup production for individual colonies was estimated from the series of counts using a maximum likelihood model. At 3 colonies, 2 in England, annual pup production was estimated using ground counts. Between the early 1960s and the early 1990s, grey seal pup production progressively increased. At colonies in the Inner and Outer Hebrides, production appeared to stabilize during the 1990s and has remained so. Pup production at colonies in Orkney and in the North Sea has continued to increase but in recent years the rate of increase has declined. This may imply that the UK grey seal population is reaching some limit to its size. The observed changes in pup production imply that some density dependent factors are affecting the British grey seal population. Changes in either juvenile survival and/or female fecundity are the most likely options. Without knowing which of these, or what combination of these factors, is operating, estimating total population size is complicated.

From pup production to quotas: current status of harp seals in the Greenland Sea

Abstract Harp seals (Pagophilus groenlandicus) have been harvested for centuries in the North Atlantic. Estimating abundance and monitoring changes in population size are critical for the management of the species. In March 2012, the harp seal pup production was estimated from aerial photographic surveys over the whelping areas. A total area of 305 km2 was photographed and 6034 pups were counted on the photos. From this the total pup production estimate was 89 590 ( s.e. = 12 310, CV = 13.7%). The status of the stock was subsequently assessed by fitting a population model to the independent pup production estimate, the historical catch data, and the historical reproduction data. The 2013 total abundance (including pups) was estimated to be 627 410 (95% CI = 470 540–784 280) harp seals. We demonstrate how the model is used in assessment when exploring the effect of various catch scenarios on future predictions.

Methods for estimating spatial trends in Steller sea lion pup production using the Kalman filter

Many species exhibit spatially varying trends in population size and status, often driven by differences among factors affecting individual subpopulations. Estimation and differentiation of such trends may be important for management, and a driving force for monitoring programs. The ability to estimate spatial differences in population trend may depend on assumptions regarding connectivity among subpopulations (stock structure or spatial overlap in stressors), information that is often poorly known. Linear state-space models using the Kalman filter were developed, tested, and applied for trend estimation of pup production for the western Alaska stock of Steller sea lions (Eumetopias jubatus), given only count data. Models were able to estimate trends and abundance even when data were missing. Models that assumed spatial correlation in trend among rookeries were more robust to stock structure assumptions when the stock structure was potentially mis-specified. High levels of spatial correlation among rookeries estimated from Steller sea lion pup count data are consistent with large-scale covariance of population trend within the Steller sea lion metapopulation.

Incorporating density dependence in pup production in a stock assessment of NE Atlantic spurdog Squalus acanthias

Abstract De Oliveira, J. A. A., Ellis, J. R., and Dobby, H. 2013. Incorporating density dependence in pup production in a stock assessment of NE Atlantic spurdog Squalus acanthias. – ICES Journal of Marine Science, 70: . An age- and sex-structured stock assessment model for Northeast Atlantic spurdog Squalus acanthias is presented that includes length-based processes, such as maturation, pup production, growth, and gear selectivity, with a length-at-age relationship to convert length to age. It relates pup production functionally to numbers of pregnant females, allowing for density-dependent effects. The model was fitted to a combined Scottish groundfish survey biomass index, to proportion-by-length category data from both trawl surveys and commercial catch sampling from target and non-target fisheries, and to fecundity data. The model was run from 1905 to better reflect virgin conditions and to allow early fecundity data to be fitted in order to estimate the extent of density dependence in pup production. The model estimated 2010 population levels to be about 23% relative to 1955 and 19% relative to 1905. Results confirm that the stock is depleted, but not to the extent estimated in a previous assessment. Current estimates of depletion would support an IUCN listing of “Endangered”, but not “Critically Endangered”. Model projections showed that a TAC of 1422 t (the last non-zero TAC) would allow future population growth.

Assessment of Caspian Seal By-Catch in an Illegal Fishery Using an Interview-Based Approach

The Caspian seal (Pusa caspica) has declined by more than 90% since 1900 and is listed as endangered by IUCN. We made the first quantitative assessment of Caspian seal by-catch mortality in fisheries in the north Caspian Sea by conducting semi-structured interviews in fishing communities along the coasts of Russia (Kalmykia, Dagestan), Kazakhstan and Turkmenistan. We recorded a documented minimum by-catch of 1,215 seals in the survey sample, for the 2008–2009 fishing season, 93% of which occurred in illegal sturgeon fisheries. Due to the illegal nature of the fishery, accurately quantifying total fishing effort is problematic and the survey sample could reflect less than 10% of poaching activity in the north Caspian Sea. Therefore total annual by-catch may be significantly greater than the minimum documented by the survey. The presence of high by-catch rates was supported independently by evidence of net entanglement from seal carcasses, during a mass stranding on the Kazakh coast in May 2009, where 30 of 312 carcasses were entangled in large mesh sturgeon net remnants. The documented minimum by-catch may account for 5 to 19% of annual pup production. Sturgeon poaching therefore not only represents a serious threat to Caspian sturgeon populations, but may also be having broader impacts on the Caspian Sea ecosystem by contributing to a decline in one of the ecosystem’s key predators. This study demonstrates the utility of interview-based approaches in providing rapid assessments of by-catch in illegal small-scale fisheries, which are not amenable to study by other methods.

Functional relationship between harp seal body condition and available prey in the Barents Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 484:287-301 (2013) - DOI: https://doi.org/10.3354/meps10272 Functional relationship between harp seal body condition and available prey in the Barents Sea Tor Arne Øigård1,*, Ulf Lindstrøm1, Tore Haug1, Kjell Tormod Nilssen1, Sophie Smout2 1Institute of Marine Research, PO Box 6404, 9294 Tromsø, Norway 2Sea Mammal Research Unit, Scottish Oceans Institute, University of St. Andrews, St. Andrews, Fife KY16 8LB, UK *Email: tor.arne.oeigaard@imr.no ABSTRACT: The Barents Sea ecosystem has undergone substantial ecological fluctuations over the past 40 yr, including large variations in the abundance of capelin Mallotus villosus, herring Clupea harrengus, krill Thysanoessa sp. and Meganyctiphanes norvegica, polar cod Boreogadus saida, and Atlantic cod Gadus morhua. There is evidence to suggest that harp seals Pagophilus groenlandicus have responded to these changes. The current study analysed the relationships between harp seal body condition, environmental variables and the biomass of major harp seal prey. Harp seal body condition was estimated from samples taken in the southeastern Barents Sea during spring from 1992 to 2011. Body condition of juveniles and adults varied between years, improving from 1992 until 2001 and later deteriorating, with weakest condition in 2011. We investigated covariates that might explain such interannual variation. Significant relationships were found between harp seal blubber thickness and prey abundances. High abundances of capelin, polar cod and Atlantic cod had a negative impact on condition, whereas high abundance of krill had a positive impact. Environmental covariates did not improve the models, probably because these were strongly correlated with prey abundance. We also found a correlation between pup production and blubber thickness, indicating that observed declines in pup production may be associated with decreased body condition of the seals. We further show that competitive interactions in the food web (e.g. competition between harp seals and some of their prey for shared resources, such as krill) may result in unexpected negative predator–prey relationships. This has implications for predator breeding success and population dynamics. KEY WORDS: Harp seal · Predator–prey · Body condition · Barents Sea · Prey availability · Prey quality · Generalised additive model Full text in pdf format Supplementary material PreviousCite this article as: Øigård TA, Lindstrøm U, Haug T, Nilssen KT, Smout S (2013) Functional relationship between harp seal body condition and available prey in the Barents Sea. Mar Ecol Prog Ser 484:287-301. https://doi.org/10.3354/meps10272 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 484. Online publication date: June 12, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Bayesian Clustering of Animal Abundance Trends for Inference and Dimension Reduction

We consider a model-based clustering approach to examining abundance trends in a metapopulation. When examining trends for an animal population with management goals in mind one is often interested in those segments of the population that behave similarly to one another with respect to abundance. Our proposed trend analysis incorporates a clustering method that is an extension of the classic Chinese Restaurant Process, and the associated Dirichlet process prior, which allows for inclusion of distance covariates between sites. This approach has two main benefits: (1) nonparametric spatial association of trends and (2) reduced dimension of the spatio-temporal trend process. We present a transdimensional Gibbs sampler for making Bayesian inference that is efficient in the sense that all of the full conditionals can be directly sampled from save one. To demonstrate the proposed method we examine long term trends in northern fur seal pup production at 19 rookeries in the Pribilof Islands, Alaska. There was strong evidence that clustering of similar year-to-year deviation from linear trends was associated with whether rookeries were located on the same island. Clustering of local linear trends did not seem to be strongly associated with any of the distance covariates. In the fur seal trends analysis an overwhelming proportion of the MCMC iterations produced a 73–79 % reduction in the dimension of the spatio-temporal trend process, depending on the number of cluster groups.

Reproductive correlates of social network variation in plurally breeding degus (Octodon degus)

Studying the causes and reproductive consequences of social variation can provide insight into the evolutionary basis of sociality. Individuals are expected to behave adaptively to maximize reproductive success, but reproductive outcomes can also depend on group structure. Degus (Octodon degus) are plurally breeding rodents, in which females allonurse indiscriminately. However, communal rearing does not appear to enhance female reproductive success, and larger group sizes are correlated with decreasing per capita pup production. To further investigate mechanisms underlying these patterns, we asked how differences in sex, season and average group reproductive success are related to degu association networks. We hypothesized that if reproductive differences mirror social relationships, then females (core group members) should show stronger and more stable associations than males, and female association strength should be strongest during lactation. We also hypothesized that, at the group level, social cohesion would increase reproductive output, while social conflict would decrease it. Females did have higher association strength and more preferred partners than males, but only during lactation, when overall female associations increased. Females also had more stable preferred social partnerships between seasons. A measure of social cohesion (average association strength) was not related to per capita pup production of female group members, but potential social conflict (heterogeneity of association strengths) was negatively related to per capita pup production of female group members. Our results highlight temporal and multilevel patterns of social structure that may reflect reproductive costs and benefits to females.

When aerial surveys will not do: grey seal pup production in cryptic habitats of Wales

Grey seals (Halichoerus grypus) are a species of conservation concern that require Marine Protected Area management and population status assessment under the EU Habitats Directive. Aerial surveys are commonly used to monitor grey seal pup production at their globally important UK colonies. However, in Wales more than half of pups are born in cryptic breeding habitats such as sea caves. These cryptic habitats preclude the use of aerial monitoring methods and necessitate ground-based counts, which are costly in resources. In this study, we compare a ground-based pup production census with a reduced effort plot-sampling survey to estimate pup production, derive a total population size and assess cost effectiveness. Pup production in North Wales was estimated at 91 (95% confidence interval: 70–112) by the plot-sampling design and was a good approximation of the ‘true’ value of 96 derived from the census. The total population size in North Wales was estimated at between 242 and 307 grey seals. The plot-sampling design reduced survey effort by 46% and saved 30% on logistical costs compared to the full census. We outline the suitability of this method as part of a monitoring programme for grey seal pup production and suggest our approach may be applicable to other regions where grey seals use cryptic breeding habitat.

High FSH decreases the developmental potential of mouse oocytes and resulting fertilized embryos, but does not influence offspring physiology and behavior in vitro or in vivo

Do different concentrations of FSH in the assisted reproductive technology (ART) procedure in vitro or in vivo affect the developmental competence of oocytes, the embryos and the offspring conceived from these embryos? Improper FSH treatment (200 IU/l in vitro, 10 IU/ml in vivo and 200 IU/ml in vivo) impairs the development competence of oocyte and embryo, but does not influence offspring physiology and behavior. Exogenous FSH has been widely used in the field of ART. However, the effects of different concentrations of FSH on the developmental competence of oocytes, embryos and the offspring conceived from these embryos, are still unknown. In a prospective study, a total of 45 mice at 8-10 weeks of age were primed in vivo with different dosages of FSH (9 mice in the 10 IU/ml, 10 mice in the 50 IU/ml, 10 mice in the 100 IU/ml and 16 mice in the 200 IU/ml groups). Fresh MII oocytes were retrieved from ovaries: this was designated as in vivo group. Thirty six mice at 8-10 weeks of age were sacrificed by cervical dislocation to obtain ovaries without FSH treatment (9 mice in the 0 IU/l, 9 mice in the 50 IU/l, 8 mice in the 100 IU/l and 10 mice in the 200 IU/l groups), and then the immature oocytes were collected from these ovaries and cultured in vitro matured medium supplemented with 0, 50, 100 and 200 IU/l FSH: this was designated as in vitro group. Spindle assembly of matured MII oocytes was stained via an immunofluorescence method and the oocytes ratio of normal spindle was analyzed. The developmental competence of the resulting fertilized embryos in the pre- and post-implantation stages was examined in in vitro and in vivo groups. Furthermore, physiological index, including reproductive potential and body weight, of the offspring was investigated by mating experiments and behavior index, including learning, memory, probing and intelligence, was tested by Morris water maze in in vitro and in vivo groups. In the in vitro groups, the oocyte maturation competence, normal spindle assembly, blastocyst formation and implantation, as well as viable pup production were all impaired in the group treated with 200 IU/l FSH (P < 0.05). No differences were observed among the other three groups (P > 0.05). In the in vivo groups, 10 IU/ml FSH but not 200 IU/ml treatment influenced blastocyst formation and viable pup production (P < 0.05), although the high proportion of spindle assembly abnormality was only observed in the 200 IU/ml FSH treatment group (P < 0.05). Furthermore, there were no significant differences in terms of physiological index (reproductive potential and body weight) and behavior index (learning, memory, probing and intelligence) in offspring from in vitro and in vivo groups (P > 0.05). The mouse model was used in this study. The results of the mouse follicle growth and oocyte development in responding to different concentrations of FSH are not 100% transferable to human, because of the physiological differences between mouse and human. The findings indicated that FSH application in the field of ART is safe to the resulted offspring, but it should be more carefully used for each women in ART cycles because the inappropriate FSH concentration would decrease the oocyte developmental competence. This work was partially supported by the Ministry of Science and Technology of China Grants (973 program; 2011CB944504), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (30825038), the National Natural Science Funds for Young Scholar (31000661) and by the Joint Research Fund for Overseas, Hong Kong and Marco Scholars (31128013/C120205). None of the authors has any conflicts of interest.

Decline and Extermination of an Arctic Wolf Population in East Greenland, 1899–1939

The decline and extermination of an arctic wolf population in East Greenland between 1899 and 1939 were investigated through analysis of 40 years of archival data, which contained records of 252 sightings of wolves or their tracks. Prior to the start of exploitation by Europeans, this small, isolated wolf population probably consisted of about 38 wolves during an average year. Of 112 wolves sighted in early winter, 31.3% were lone wolves, 23.2% were in pairs, and the rest were in larger groups. Mean pack size was 3.3 wolves, and packs of more than four wolves were rare. The population was concentrated in the central part of its range, making it vulnerable to exploitation by Danish and Norwegian commercial hunters, who exterminated the population. Poison was the primary agent of destruction. There was no evidence that other proposed causes of the decline were influential. This study provided the first evidence of an arctic wolf population that was eradicated and highlights the vulnerability of small, isolated wolf populations to excessive harvest. Wolves in the High Arctic may be particularly vulnerable because of their exceptionally low densities, smaller pack sizes, lower pup production, infrequent reproduction, and insular or disjunct distributions.

Using life‐history traits of New Zealand sea lions, Auckland Islands to clarify potential causes of decline

AbstractAnnual censuses of New Zealand (NZ) sea lions Phocarctos hookeri at the subantarctic Auckland Islands have indicated a decline in pup production of over 40% during the first decade of the 2000s. With this significant decline and likely decline in the population as a whole, population ecology theory hypothesizes that life‐history traits such as reproduction rate, survival or growth should improve, particularly if density‐dependency is playing a significant role in the population. This research examined whether changes in NZ sea lion pup production were associated with changes in adult abundance or population life‐history traits in an attempt to clarify potential causes of decline. Since 1998/1999, daily surveys of Sandy Bay, Enderby Island, were undertaken during the NZ sea lion breeding season (December–February). These surveys confirm that the number of adults at the breeding area has significantly declined during the period of pup production decline. There was no difference between years in mean pup birth date, but the ratio of pups to females ashore during peak pupping varied significantly. The sex ratio of pups at birth also varied from year to year, but with no significant variation overall. Pup mortality varied significantly only during years of epizootic events (1997/1998, 2001/2002 and 2002/2003). Pup birth mass showed little variation between 2000/2001 and 2006/2007, increasing slightly in the last 3 years of study. Pup mass at 3 weeks, although highly variable, showed no trend during the period of decline. Despite the significant decrease in pup production and breeding animals, not all life‐history traits relating to pup mass and survival or female fecundity improved. Research suggests that indirect fishing‐related pressures may influence some of these traits and that the NZ sea lion population was unlikely to have been influenced by density‐dependent factors or to have been at or near carrying capacity before the decline.

Increasing pup production of New Zealand sea lions at Campbell Island/Motu Ihupuku: can it continue?

New Zealand (NZ) sea lions (Phocarctos hookeri) were relisted as ‘nationally critical’ by the New Zealand Government in 2010, owing to recent severe declines in pup production at the Auckland Islands. However, research on Campbell Island/Motu Ihupuku indicates that this population's pup production is increasing. Between December 2009 and February 2010, surveys were undertaken aiming to determine production and early mortality rates (up to eight weeks) of NZ sea lion pups on Campbell Island. In total, 402 pups were tagged and a minimum pup production of 681 estimated from direct count. This estimate is 17% higher than the 2008 estimate of 583 pups and equates to 27% of the total pup production of the NZ sea lions in 2009–10. However, early pup mortality (55%) continues to be the highest recorded for any NZ sea lion breeding area and it is hypothesised that this breeding area is unlikely to be able to maintain this pup production increase.

Estimating pup production in a mammal with an extended and aseasonal breeding season, the Australian sea lion (Neophoca cinerea)

Context The Australian sea lion population at Seal Bay Conservation Park, South Australia, was estimated to be declining at a rate of 1.14% per breeding season, on the basis of maximum counts of live pups in each of 13 breeding seasons (Shaughnessy et al. 2006). The reliability of the pup-production estimates used to identify this decline is uncertain. Aims Our aims were to obtain representative and repeatable estimates of pup production and to assess the current rate of decline. Methods We compared four estimates of pup abundance over five breeding seasons (2002–03, 2004, 2005–06, 2007, 2008–09), including the count of cumulative new births, the maximum live-pup count, the number of pups given passive integrated transponder (PIT) tags, and mark–recapture methods using the Petersen estimate. Key results A total of 90% of pup births occurred over a mean of 124 days (s.d. = 14). Final estimates of pup production (from the largest of the four estimation methods used) in the five seasons were 227 (CL 221–239), 288 (CL 273–302), 219 (NA), 260 (CL 254–272) and 268 (CL 268–269). The average estimate of pup mortality was 28.6% (s.d. = 6.3%). The decline in the population at Seal Bay over 17 breeding seasons on the basis of maximum counts of live pups was 0.51% per year or 0.76% per breeding season. However, this trend was not based on best estimates of pup production. On the basis of final estimates for the last five breeding seasons, there is no declining trend. Conclusions The count of cumulative new births was the most reliable measure of pup production; the Petersen mark–recapture estimate provided a check for accuracy and confidence limits about the estimate. Implications The actual rate of change and the expected trajectory of the Seal Bay population remain uncertain. Ongoing monitoring is a priority for this site, using the reliable methods of estimating pup production identified in the present study.

Relation between reproduction and fat reserves in female muskrat (Ondatra zibethicus)

The production and care of offspring by female mammals imposes substantial energetic costs. Muskrat ( Ondatra zibethicus ) is an iteroparous mammal that can produce multiple litters annually. We investigated the relation between body fat and pup production in female muskrat. There were significant negative relations between percent body fat and total number of placental scars (i.e., embryos produced) and the number of litters produced. Reduction in body fat might have resulted from reproductive effort and might decrease future survival and reproduction in muskrat.

Population viability analysis of New Zealand sea lions, Auckland Islands, New Zealand’s sub-Antarctics: assessing relative impacts and uncertainty

A common issue faced in wildlife management is how to assess the uncertainty of potential impacts on the viability of a species or population. The pup production of New Zealand (NZ) sea lions (Phocarctos hookeri) has declined 50% in the last 12 years at their main breeding area, the Auckland Islands. The two major known atypical impacts on NZ sea lions are as follows: (1) the direct mortality as bycatch of trawling and (2) bacterial epizootics, which can affect reproduction and mortality. Both of these impacts include high levels of uncertainty, with fisheries data being variable due to percentage observer coverage and the effect of sea lion exclusion devises, while the timing and severity of bacterial epizootics are not predictable. In this paper, an age-structured model of the NZ sea lion population at the Auckland Islands was built to examine the predicted effects of fisheries mortality and catastrophes (bacterial epizootics), both separately and then combined, on population viability over a 100-year period using the VORTEX population viability analysis programme. These models are then compared against 15 years of empirical field data to determine the actual level of impacts being observed. Model results indicate that although naturally occurring epizootics reduce the growth rate of the population, it does not cause a decline in the Auckland Island population. However, sustained fisheries bycatch at current estimated levels, particularly considering its potential impact on adult female survival, could result in a population decline and possible functional extinction over the modelled time period.

The Northern Elephant Seal (Mirounga angustirostris) Rookery at Año Nuevo: A Case Study in Colonization

Our aim was to examine the colonization process in a large mammal, documenting the development of a breeding colony from its inception to reaching equilibrium numbers. We describe the development of a colony of northern elephant seals (Mirounga angustirostris) at Ano Nuevo in central California from initial colonization in 1961 to 2010, a period when the worldwide population was expanding rapidly. We recorded pup production and pup mortality prior to weaning from censuses of animals by sex and age categories. Colony growth was rapid initially, and pup production reached approximately 2,700 births during the period 1995 to 2006. Pups born declined subsequently. The pattern of colony growth and decline is explained by species-specific seal behavior; population variables that influence immigration rates; and local environmental factors such as breeding space, animal density, and tidal and surf conditions at peak season that increase pup mortality. Colony growth was driven primarily by external recruitment of young females from large southern rookeries rather than internal recruitment. Births on the island segment of the colony, where breeding space was limited, peaked in 1980 then declined subsequently by 50% in association with increased density and pup mortality. Births on the adjacent mainland stabilized from 1995 to 2006, despite ample breeding space and low pup mortality; cessation of growth here was associated with reduced external recruitment of females. Primiparous females pioneer the establishment of new colonies, settling new sites to avoid low weaning success in crowded natal rookeries where they are dominated by older females. We conclude that the long-term study of the development of a single colony provides vital information on colony and population processes that have wide applicability to other mammals. The colonization of Ano Nuevo recapitulated the process employed at other colonies during the recent growth and expansion of the population and signals the pattern to be expected in future colonies.

Causes of mortality in South American fur seal pups (Arctophoca australis gracilis) at Guafo Island, southern Chile (2004–2008)

AbstractAs part of population dynamics studies of the South American fur seal (Arctophoca australis gracilis) rookery at Punta Weather in Guafo Island (43°36'S, 74°43’W), the causes and extent of pup mortality were monitored. During four breeding seasons, daily counts of live and dead pups were carried out to determine pup production and pup mortality. Dead pups were retrieved from the rookery to perform necropsies. The mean pup production was 1,735.5 ± 336 pups and the mean pup mortality up to 12 wk old was 6.0%± 2.6%. The major causes of death were enteritis with microscopic lesions of bacteremia (28.4%), starvation (23.5%), drowning (21%), trauma (19.8%), and stillbirths (2.5%). Enteritis with microscopic lesions of bacteremia, and starvation had higher incidence during January (beginning and middle of the breeding season) while most trauma and drowning occurred during February (end of the breeding season). In the 2006–2007 breeding season there was an increase in mortality due to starvation and trauma. Most pup deaths at Guafo Island are generated by extrinsic factors; therefore, additional studies that assess the impact of environmental changes and fishing activities, are needed in order to determine the exact causes of the decline of this species along Chilean coasts.