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Allometric analyses of sexually selected structures have revealed many patterns of evolutionary and behavioural significance, for example, in weapons, ornaments, and genitalia. We investigated allometry of the baculum (penis bone) relative to body size in post-growth adults of three large mustelids: wolverine (Gulo gulo (Linnaeus, 1758)), northern river otter (Lontra canadensis (Linnaeus, 1758)), and sea otter (Erihydra lutris (Linnaeus, 1758)). The baculum grew over a longer period than did body size. Correlations among bacular variables were positive in post-growth adults. No regression slopes expressed positive allometry (i.e., slope > 1 for linear variables). These trends point to the possibility that bacular size is adapted to the average size of the reproductive tract of sexually mature female northern river otters and possibly sea otters, and that pre-ejaculatory ('precopulatory') selection is highest in those species. Bacular size varied more than skull or limb-bone size, and bacular shape also varied greatly. Species differed in size and complexity of the urethral groove and bacular apex, suggesting functional differences in intromission. Substantial variation in bacular shape resulted from healed fractures, especially in sea otter. Knowledge of copulatory behaviour, age of breeding, female reproductive anatomy, and genitalic interactions during intromission is needed for comprehensive understanding of bacular anatomy, allometry, and variation for these species. Key words: allometry, baculum, Mustelidae, museum collections, os penis, sexual selection, Introduction Darwin (1871) noted that sexually selected traits of animals often are striking or extreme, and typically vary considerably within, and across, conspecific populations and related species. Innumerable studies have [...]

In a recent review of the status of the Northwest Atlantic harp seal population, model fit to aerial survey estimates of pup production and annual reproductive rates was poor compared to previous assessments indicating underlying problems relating to model assumptions and/or structure. In this study, a new hierarchical Bayesian state-space model was fitted to the same data on pup production, annual fecundity, human removals, and environmental conditions used in the previous assessment to produce annual estimates of pup production and total abundance from 1952-2019. Data on age structure based upon random samples were also included, and the process model incorporated environmental stochasticity and several other improvements. The new model estimates were similar to the previous model through 1990 but then diverged, indicating that the population peaked in 1997 at 6.6 million animals, almost a decade earlier than modelled in previous assessments. After a period of decline due to high catches and poor ice conditions, the new model provides an abundance estimate of 4.7 (95% Credibility Interval (CI) 3.7-5.7) million in 2019, compared to an estimate of 7.6 (95% CI 6.6-8.8) million in the last assessment. The lower estimates of recent abundance reflect higher and more variable juvenile mortality after 2000 due to a combination of density-dependent and density independent factors operating on juvenile survival. The new model also suggests a decline in equilibrium abundance (K) levels from 7.6 (95% CI=7.4 to 7.8) million Northwest Atlantic harp seals prior to 2000 to 6.8 (95% CI=6.7 to 6.9) million animals post-2000. [ABSTRACT FROM AUTHOR]

Aerial surveys were completed to estimate northwest Atlantic grey seal (Halichoerus grypus) pup production in eastern Canada during December 2020 to February 2021. These surveys underestimate pup production if animals are born after the surveys are flown or if pups leave the breeding site before it is surveyed. Past assessments have modelled the distribution of births to correct this bias by fitting the proportion of animals in different morphometrically defined stages of fixed duration to a gamma or Weibull distribution (Myers Birth Distribution [MBD] Model). A new Bayesian modelling approach was developed and compared with the MBD model to examine how this approach impacts our understanding of the timing of births. Assuming that animals are weaned at 20 days of age, the model was also applied to determine the proportion of animals that were weaned and thus available to harvesters at different colonies. The MBD and Bayesian models showed similar estimates when applied to the data rich dataset acquired on Sable Island. At other breeding sites, the Bayesian model tended to estimate a slightly shorter period of births compared to the MBD model, resulting in a higher estimated proportion of animals born on the aerial survey date, and thus a smaller adjustment of counts. The weaning date estimated with the Bayesian model showed a general trend starting off the Nova Scotia coast then moving into the Gulf of St. Lawrence. The model estimated that 50% of the grey seal pups were weaned by January 6, 2021 on the southwestern Nova Scotia Islands, and on January 24 in the southern Gulf. Application of the Bayesian model to staging data acquired at several colonies in previous years showed that the date when 50% of the pups are weaned has advanced by approximately one day each year since the early 2000s in the Gulf. This trend was less clear outside the Gulf, but the timing of births in 2021 was also estimated to be earlier than in previous years. The Bayesian model provides an approach to consider several sources of uncertainty not previously taken into account. These include uncertainty associated with the date of first birth, the development stage duration, and variability in classification of stages by the various observers. By updating priors, the model can make use of new information as it is collected. The use of the Bayesian model should lead to improved estimates of population size. [ABSTRACT FROM AUTHOR]

More than 2500 ovaries were collected from Northwest Atlantic hooded seals (Cystophora cristata (Erxleben, 1777)) in the period 1956-2006 during moulting (data blocks: 1956-1960, 1970-1972, 1978), postmoulting (data blocks: 1990-1994, 1996-2006), and whelping (data blocks: 1967-1972, 1973-1976, 1979, 1983-1987, 1989-1995). Mean age at primiparity (MAP) was estimated as the mean age of females with a single corpus albicans or a corpus luteum from a post-implantation pregnancy. MAP was stable at 4.2-4.5 years during 1956-1978, increasing to 4.9-5.2 years in 1979 and to 6.1 years in 1989-1995 (later data insufficient). Patterns of corpus accumulation indicated occasional skipped pregnancies. This may have affected the accuracy of MAP estimates but not the main trends. Declining proportions of parae younger than 10 years after 1979 are consistent with effects of delayed maturation, reduced adult hunting mortality, and (or) increased juvenile mortality. From the 1990s, declining adult pregnancy rates are suggested by decreasing trends in proportions of older multiparae (8+) and other ovary-based proxies for pregnancy rates. Hooded seal abundance was largely stable from 1960 to the mid-1990s and changes in population parameters over this period are therefore more likely due to effects of ecosystem change on per-capita resource levels than population-mediated density dependence. Key words: Cystophora cristata, age at primiparity, age at maturity, mean maternal age, Northwest Atlantic. Plus de 2500 ovaires ont ete preleves chez des phoques a capuchon (Cystophora cristata (Erxleben, 1777)) du nord-ouest de l'Atlantique, durant la periode de 1956-2006 pendant la mue (blocs de donnees : 1956-1960, 1970-1972, 1978), apres la mue (blocs de donnees : 1990-1994, 1996-2006) et durant la mise bas (blocs de donnees : 1967-1972, 1973-76, 1979, 1983-1987, 1989-1995). Nous avons estime l'age moyen a la primiparite (MAP) comme etant l'age moyen des femelles possedant un seul corps blanc ou un corpus jaune d'une grossesse postimplantatoire. Le MAP est stable a 4,2-4,5 annees durant la periode de 1956-1978, puis augmente a 4,9-5,2 ans en 1979 et a 6,1 ans en 1989-1995 (les donnees subsequentes sont insuffisantes). Le patron d' accumulation des corps indique qu' ilyaal'occasion des grossesses sautees. Cela peut avoir affecte la precision des estimation du MAP, mais non les tendances principales. Les proportions declinantes de femelles de moins de 10 ans ayant ete enceintes apres 1979 concordent avec les effets de la maturation retardee, de la mortalite reduite des adultes due a la chasse et(ou) de la mortalite accrue des jeunes. A partir des annees 1990, le declin des taux de grossesse des adultes est indique par des tendances a la baisse des proportions de multipares plus agees (8+) et des autres variables de rechange basees sur les ovaires pour les taux de grossesse. L'abondance des phoques a capuchon est demeuree stable de 1960 jusqu'au milieu des annees 1990; les changements dans les variables demographiques pendant cette periode sont donc vraisemblablement dus aux effets des modifications de l'ecosysteme sur les niveaux de ressources par individu plutot qu'a une densite dependance reliee a la population. Mots-cles : Cystophora cristata, age a la primiparite, age a la maturite, age maternel moyen, nord-ouest de l'Atlantique. [Traduit par la Redaction], Introduction Hooded seals (Cystophora cristata (Erxleben, 1777)) are among the most abundant pinnipeds in the North Atlantic, with abundances currently estimated at about 600 000 in the Northwest Atlantic (NWA) [...]

In this paper, we estimate the pup production of harp seals (Pagophilus groenlandicus) using generalized additive models (GAMs) based on thin-plate regression splines. The spatial distribution of seal pups in a patch is modelled using GAMs, and the pup production is estimated by numerically integrating the model over a fine grid area of the patch. Closed form expression for estimation of the the standard error of the pup production estimate is derived. The estimators are applied to simulated seal populations to investigate their properties. The results show that the proposed pup production estimator is comparable with the conventional pup production estimator. However, the bias of the standard error estimator of the proposed method is much lower than the bias of the conventional standard error estimator. The decrease of standard error bias results in a considerable reduction of the coefficient of variation estimate using the proposed GAM-based method. The proposed method is also applied to real survey data of harp seals obtained from aerial surveys in the Greenland Sea pack ice in 2002. We show that the number of pups counted from aerial photographs possess a good fit to the negative binomial distribution when a logarithmic link function is applied. The approach described here is applicable to many situations where georeferenced counts or measurements are available. Nous estimons, dans ce travail, la production de petits chez les phoques du Groenland (Pagophilus groenlandicus) a l'aide de modeles additifs generalises (GAMs) bases sur des splines de regression en plaque mince. Nous modelisons la repartition spatiale des jeunes phoques dans une parcelle a l'aide de GAMs et nous estimons la production de jeunes en integrant le modele numeriquement sur une surface en grille fine de la parcelle. Nous derivons une expression en forme fermee pour estimer l'erreur type de l'estimation de la production de jeunes. Les estimateurs sont appliques a des populations simulees de phoques afin d'en etudier les proprietes. Les resultats montrent que l'estimateur propose de production des jeunes se compare a l'estimateur courant de production de petits. Cependant, le biais de l'estimateur de l'erreur type de la methode proposee est beaucoup plus faible que celui de l'estimateur courant de l'erreur type. La reduction du biais de l'erreur type a pour resultat une reduction considerable de l'estimation du coefficient de variation en utilisant la methode proposee basee sur les GAM. Nous avons aussi utilise la methode proposee avec de vraies donnees d'inventaire de phoques du Groenland obtenues par releves aeriens sur la banquise de la mer du Groenland en 2002. Nous demontrons que le nombre de petits denombres sur les photographies aeriennes s'ajuste bien a la distribution binomiale negative lorsqu'on utilise une fonction log-link. La methodologie que nous decrivons s'applique a de nombreuses situations dans lesquelles des denombrements ou des mesures georeferences sont disponibles. [Traduit par la Redaction], Introduction Scientific advice for the management of exploited resources is based on biological assessments. The ice breeding harp (Pagophilus groenlandicus) and hooded (Cystophora cristata) seals are both abundant species in [...]

Individuals of different age, sex, and morphology are expected to exhibit differences in dietary niches largely owing to sexual dimorphism, ontogenetic niche shifts, and resource polymorphism. Harp (Pagophilus groenlandicus (Erxleben, 1777)) and hooded (Cystophora cristata (Erxleben, 1777)) seals are geographically overlapping and highly migratory predators in the North Atlantic Ocean. These species differ in their diving behaviour, with hooded seals diving deeper, longer, and more associated with the continental shelf edge and deep ocean than harp seals. We examined blubber fatty acid (FA) composition (N = 37; 93% of total FA by mass) of harp (adults N = 294; juveniles N = 232) and hooded (adults N = 118; juveniles N = 38) seals to test hypotheses about sources of intrinsic (age and sex) and extrinsic (geographic location, season, year) variations in diets. A significant difference in FA profiles suggested dietary segregation between species. We found significant effects of sex and age class on FA profiles, with these being more pronounced in the highly size-dimorphic hooded seals than in harp seals. FA profiles of both species also varied between inshore and offshore sampling locations and between prebreeding and postbreeding periods. Finally, FA profiles of harp seals differed among years, which was coincident with large changes in prey distribution and availability in the mid-1990s. On s'attend a ce que des individus differents par l'age, le sexe ou la morphologie possedent aussi des differences de niche alimentaire principalement a cause du dimorphisme sexuel, des changements ontogeniques de niche et du polymorphisme des ressources. Les phoques du Groenland (Pagophilus groenlandicus (Erxleben, 1777)) et les phoques a capuchon (Cystophora cristata (Erxleben, 1777)) sont des predateurs fortement migrateurs de l'Atlantique Nord dont les aires de repartition geographique se chevauchent. Ces especes different dans leur comportement de plongee, les phoques a capuchon faisant des plongees plus profondes, plus longues et plus fortement associees au bord du plateau continental et a l'ocean profond que les phoques du Groenland. Nous avons analyse la composition en acides gras (FA) du lard (N = 37; 93 % en masse des FA totaux) de phoques du Groenland (N = 294; jeunes N = 232) et de phoques a capuchon (N = 118; jeunes N = 38) afin de tester des hypotheses sur les sources intrinseques (age et sexe) et extrinseques (position geographique, saison, annee) de variation du regime alimentaire. Une difference significative entre les profils de FA laisse croire a une segregation alimentaire entre les deux especes. Il existe des effets significatifs du sexe et de la classe d'age sur les profils de FA qui sont plus prononces chez le phoque a capuchon qui affiche un fort dimorphisme de la taille que chez le phoque du Groenland. Les profils de FA des deux especes different aussi entre les sites d'echantillonnage du bord et du large, ainsi que durant les periodes avant et apres la reproduction. Enfin, les profils de FA du phoque du Groenland varient entre les annees, ce qui coincide avec les importants changements dans la repartition et la disponibilite des proies qui se sont produits au milieu des annees 1990. [Traduit par la Redaction], Introduction Diet has important consequences for gross energy intake, foraging costs, and exposure to foraging-specific risk factors such as predation and competition (Bolnick et al. 2003). Interspecific competition for prey [...]

The northwest Atlantic subspecies of gray seal (Halicheorus grypus grypus) has been increasing for more than a half century and has reestablished breeding colonies in Canadian and US waters. In 2016, visual, oblique, and vertical large‐format digital photographic surveys were conducted at all known breeding colonies in the northwest Atlantic. Total pup production in the northwest Atlantic was estimated to be 109,000 (SE = 17,500) pups. At 87,500 (SE = 15,100) pups, Sable Island accounts for 80% of total pup production. Regional differences in pup production trends are evident. Pup production in the Gulf of St. Lawrence and along the eastern shore of Nova Scotia has been relatively stable. Since 2004, the rate of increase in pup production at Sable Island has slowed to about 5%–7% per year, while the newer colonies in southwest Nova Scotia and the northeastern United States are increasing rapidly. In 2016, the Muskeget Island (MA) breeding colony produced 3,900 (SE = 200) pups, making it the third largest breeding colony in the northwest Atlantic. This southward shift in production may reflect climate‐mediated changes in population growth as well as reestablishment of colonies throughout the former range associated with increased protection. [ABSTRACT FROM AUTHOR]

Harp seals require pack ice as a platform for resting, to give birth and nurse their young. They are also subject to commercial and subsistence harvesting. We examined the status of the Northwest Atlantic harp seal population using a three parameter population model that fits to estimates of pup production and reproductive rates, and incorporates information on annual catches in Canada and Greenland (including by-catch and struck and lost), and unusual pup mortality due to poor ice conditions. After applying the model formulation used during previous assessments, the fit to the reproductive data and aerial survey data was poor. Using an alternative formulation where adult mortality was fixed and juvenile mortality estimated, and a Comprehensive Environmental Index used to vary the population carrying capacity, improved the model fit to the data. Based upon a population model that included pup production estimates up to 2017, annual estimates of age-specific reproductive rates, removals and ice related mortality up to 2019, the harp seal population appears to have been relatively stable since the mid-1990s, but has been increasing in recent years likely due to higher reproductive rates and lower removals. The model estimated a pup production of 1,039,000 (95% CI 927,000 - 1,100,000) animals and a total population size of 6.8 (95% CI 5.8 - 8.0) million animals in 2017. Projecting forward to 2019, the model estimated that the population increased to 7.6 (95% CI 6.6 - 8.8) million harp seals. Climate change is having an impact on ice-cover, particularly in the Gulf of St Lawrence, but even the northeast Newfoundland area is expected to be ice-free by the end of the century. This will have a negative impact on harp seals unless new areas for pupping are found to the north of current whelping areas. [ABSTRACT FROM AUTHOR]