CHANGES IN MORPHOLOGY WITH AGE IN MEDITERRANEAN MONK SEALS (MONACHUS MONACHUS)

In order to describe the pelage and external appearance of the Mediterranean monk seal ( Monachus monachus ) and prepare an age-sex classification guide, 120 seals from the Cabo Blanco Peninsula colony in the Western Sahara/Mauritania were periodically photographed between 1993 and 1996. Analysis of the pigmentation pattern, pelage color and pattern of natural markings of each seal established 48 phenetic types, which were, in turn, arranged in five groups (morphological classes) with multivariate cluster analysis (UPGMA). The variables that best define these groups are size and color. The variation related to relative size, sex and age of 26 identified seals monitored over three years showed that: (1) after each molt, external appearance varied considerably only in non-adults, while adult appearance was invariable; (2) marked sexual dimorphism exists in adults' external appearance; and (3) a remarkable similarity of adult and neonate pelage exists. With these results, we propose an age-sex classification guide to facilitate monk seal identification in the field.     

Hematologic and serum biochemical profile of the northern elephant seal (Mirounga angustirostris): variation with age, sex, and season

The foraging success, and thus the survival and reproductive success, of deep-diving pinnipeds such as the northern elephant seal, Mirounga angustirostris, depends on the ability to withstand repetitive breath-hold dives. Health parameters can be incorporated as potential explanatory variables for differences observed in diving and migratory performance of individual seals. Furthermore, biomedical samples from apparently healthy individuals can provide valuable baseline data for evaluating effects of natural or anthropogenic threats to individuals and populations. We evaluated 42 blood parameters in 134 northern elephant seals during the breeding and molting seasons (1992-1999) to test for age, sex, and seasonal differences and to develop reference ranges. Adult males sampled during the breeding season differed from all other adult groups for a suite of parameters often associated with inflammation, infection, or other stressors: lower hematocrit, higher white blood cell count, higher band neutrophils, higher neutrophil count, lower albumin, and lower serum iron. Adult females during the breeding season differed from all other adult categories for two parameters (lower platelet counts, lower alanine aminotransferase activity). Molting males had higher blood urea nitrogen than all other classes; creatinine did not differ between breeding and molting adult males, but was higher in males than in females in both seasons. We found significant differences among age classes for 24 of 42 parameters measured, including higher levels of triglycerides, total protein, calcium, and iron in pups than we found in juveniles or adults. Unlike other mammals which undergo substantial decreases in energy expenditure during prolonged fasting (e.g., hibernation), northern elephant seals defend territories, give birth and suckle large offspring, mate, and molt during their bi-annual fasts. Nonetheless, many studies have described physiologic homeostasis during fasting in elephant seals. The genus Mirounga is superbly adapted to going without feeding for extended periods, and this is reflected in our hematologic and serum biochemical profiles.     

Demographic variation in timing and intensity of feather molt in migratory Fork‐tailed Flycatchers (Tyrannus s. savana)

Understanding the annual cycle of migratory birds is imperative for evaluating the evolution of life‐history strategies and developing effective conservation strategies. Yet, we still know little about the annual cycle of migratory birds that breed at south‐temperate latitudes of South America. We aged, sexed, and determined the progression and intensity of body, remige, and rectrix molt of migratory Fork‐tailed Flycatchers (Tyrannus s. savana) at breeding sites in southern South America and at wintering sites in northern South America. Molt of both body and flight feathers occurred primarily during the winter. In early winter, a similar proportion of young and adult flycatchers molted remiges and rectrices, but remige molt intensity (number of remiges molting) was greater and primary molt progression (mean primary feather molting) more advanced in adults. In late winter, remige molt intensity and primary molt progression did not differ between age groups. We found no difference between males and females either in the proportion of individuals molting in winter or in the intensity or progress of remige molt. Our results suggest that the nominate subspecies of Fork‐tailed Flycatcher undergoes one complete, annual molt on the wintering grounds, and represents the first comprehensive evaluation of molt timing of a migratory New World flycatcher that overwinters in the tropics. Given that breeding, molt, and migration represent three key events in the annual cycle of migratory birds, knowledge of the timing of these events is the first step toward understanding the possible tradeoffs migratory birds face throughout the year.     

Local weather and body condition influence habitat use and movements on land of molting female southern elephant seals (Mirounga leonina)

Southern elephant seals (Mirounga leonina) are known to move and aggregate while molting, but little is known about their behavior on land during this time. In this study, 60 adult females were monitored (23 with GPS tags) during four molting seasons, between 2012 and 2016 at Kerguelen Archipelago, Indian Ocean. Population surveys were recorded each year (N = 230 daily counts), and habitat use was analyzed in relation to the stage of the molt and local weather. Based on stage of molt, habitat use, and movements on land, we classified the molt of elephant seals into three phases: (1) a “search phase” at the initial stage of molt when grass and wallow habitats were used and characterized by greater mean distances travelled on land per day compared with the two other phases; (2) a “resident phase”: during initial and mid‐stage of molt when animals were found in grass and wallow habitats but with less distance moved on land; and (3) a “termination phase” at the final stage of molt where grass and beach habitats were occupied with no change in distances. Windchill and solar radiation influenced individual distances moved per day (mean 590 ± 237.0 m) at the mid‐ and final stage of molt such that animals travelled greater distances on days of low windchill or high solar radiation. Individual variation in distance moved and relative habitat use were also linked to body mass index (BMI) at arrival on the colony, as females with higher BMI moved less and preferred beach habitat. Moreover, the individual rate of molt increased with the use of wallows. Aggregation rate tended to be negatively correlated with distances moved. We therefore suggest that individuals face an energetic trade‐off while molting, balancing energy expenditure between movement and thermoregulation.     

Molting phenology of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the Baja California Peninsula,Mexico

We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt.     

DO PHOTOPERIOD AND TEMPERATURE INFLUENCE THE MOLT CYCLE OF PHOCA VITULINA IN CAPTIVITY?

Photoperiod variations are the principal environmental signals entraining circannual activity in mammals, which is also believed to be influenced by changes in temperature and nutrition. Control of the molt in phocids has not been extensively studied with experimental manipulations of environmental factors, but substantial work indicates that photoperiod has a primary influence on mammalian breeding and furring mechanisms. Studies were under taken to reestablish the molt cycle in five harbor seals ( Phoca vitulina ) previously kept in an enclosed facility with a limited air/water temperature gradient and artificial photoperiod. The seals were exposed to an extended temperature gradient during the first period of study, and no molting was observed. The second period of study was characterized by a natural occurring photoperiod of 8 h 53 min light (L)/15 h 07 min dark (D) and a maximal 15 h 31 min L/8h 29 min D duration, and molting occurred in all individuals. These results suggest a prevalent influence of photoperiod variation on the harbor seal molt.     

Correlates of molt in golden lion tamarins (Leontopithecus rosalia)

In this paper we describe the timing and correlates of molt for a native population of golden lion tamarins (Leontopithecus rosalia). We conducted 820 examinations of 267 adult tamarins over a 7.75 year period to determine the annual molting cycle in this population. Dorsal molt was an annual event for most individuals in the study population; however, 10% of sampled individuals apparently molted twice in a 12 month period. Duration of molt was estimated at 5–6 weeks. The proportion of samples in which tamarins were in molt was significantly greater during the wet season than the dry season and positively correlated with mean monthly precipitation and minimum temperature but not tamarin births, suggesting an environmental component to timing of molt. We found no sex differences in the occurrence of molt during wet or dry seasons. However, the relative frequency of samples in molt was significantly less for gravid females than for nongravid females. In four polygynous groups, socially dominant females gave birth before subordinate females, and younger reproductive females completed molt before older reproductive females. © 1995 Wiley-Liss, Inc.     

The annual cycle of molt in the Cape hare<Emphasis Type="Italic">Lepus capensis</Emphasis> in northern China: pattern,timing and duration

Molt is an important life history event for mammals occurring in temperate and cold zones. In the present paper, I investigate the pattern, timing and duration of seasonal molts of the Cape haresLepus capensis Linnaeus, 1798 in northern China, by tracing and scoring the process of each molt quantitatively. All the seasonal molts in both overwintering and juvenile hares went through a similar order: midback (together with nape), flanks, belly, upper tail, and legs. Yet, there was a relatively confused pattern of replacement during the heaviest molting period of overwintering hares, compared to a relatively uniform pattern among juvenile hares. Overwintering hares experienced a spring and a fall molt. The fall molt was already initiated prior to completion of the spring molt and had a relatively short duration. Juveniles born early in the year (before July), before their fall molt, had undergone a postnatal molt, but those born late (July to September) had not. The juvenile fall molt had already begun when the postnatal molt was at its later stages. These facts suggest that the time budget for fall molt is tight and seasonally constrained. The timing and duration of molts in the overwintering and early-born juvenile hares were independent of individual age. Among overwintering hares, both sexes started spring molt synchronously, but the females were behind the males in late period of this molt and consequently further delayed throughout subsequent fall molt. This may be related to a higher cost of reproduction in females. No sexual difference was found in the molting progress of juvenile hares.     

Harbor seal use of glacier ice and terrestrial haul‐outs in the Kenai Fjords,Alaska

Harbor seals, Phoca vitulina, use diverse haul‐out substrates including ice calved by tidewater glaciers. Numbers of seals at glacial and terrestrial haul‐outs on the southeastern Kenai Peninsula, Alaska, were assessed using aerial, vessel, and video surveys. Mean annual abundance at glacial and terrestrial haul‐outs differed temporally. From 2004 to 2011, numbers of seals counted during the molt increased 5.4%/yr at glacial haul‐outs and 9%/yr at terrestrial haul‐outs while numbers of pups increased 5.0%/yr at glacial sites and 1.5%/yr at terrestrial sites. Numbers of seals without pups counted during pupping increased 7.96%/yr at glacial sites and 5.1%/yr at terrestrial sites. Results indicate that pupping and molting locations are not equivalent and population monitoring during the molt does not necessarily reflect habitat association of pupping seals. Ratios of pups to total seals counted during pupping and the subsequent molt were used to contrast habitat use. Low proportions of pups at terrestrial haul‐outs, relative to most glacial haul‐outs, indicate an overall preference for pupping in glacial haul‐outs. High proportions of pups at most glacial sites (during pupping and molting) suggest reduced use of tidewater glacier habitats by nonbreeders and molting seals. Results suggest more seals associate with glacial haul‐outs than currently estimated.     

Effects of Age,Adipose Percent,and Reproduction on PCB Concentrations and Profiles in an Extreme Fasting North Pacific Marine Mammal

Persistent organic pollutants, including polychlorinated biphenyls (PCBs), are widely distributed and detectable far from anthropogenic sources. Northern elephant seals (Mirounga angustirostris) biannually travel thousands of kilometers to forage in coastal and open-ocean regions of the northeast Pacific Ocean and then return to land where they fast while breeding and molting. Our study examined potential effects of age, adipose percent, and the difference between the breeding and molting fasts on PCB concentrations and congener profiles in blubber and serum of northern elephant seal females. Between 2005 and 2007, we sampled blubber and blood from 58 seals before and after a foraging trip, which were then analyzed for PCBs. Age did not significantly affect total PCB concentrations; however, the proportion of PCB congeners with different numbers of chlorine atoms was significantly affected by age, especially in the outer blubber. Younger adult females had a significantly greater proportion of low-chlorinated PCBs (tri-, tetra-, and penta-CBs) than older females, with the opposite trend observed for hepta-CBs, indicating that an age-associated process such as parity (birth) may significantly affect congener profiles. The percent of adipose tissue had a significant relationship with inner blubber PCB concentrations, with the highest mean concentrations observed at the end of the molting fast. These results highlight the importance of sampling across the entire blubber layer when assessing contaminant levels in phocid seals and taking into account the adipose stores and reproductive status of an animal when conducting contaminant research.     

Modification of aggression through socialization and the special case of adult and adolescent male rhesus monkeys (Macaca mulatta)

Significant differences exist in the frequencies with which age-sex classes of rhesus macaques engage in agonistic interactions with other age-sex classes. In the study reported here, individuals engaged in significantly more agonistic interactions within their own age-sex classes, but, adult females also showed significantly more aggression toward infants and young females whereas adult males directed significantly more aggression toward adolescent males. Infants directed aggression toward infants of both sexes, but adults showed significantly less aggression toward adults of the opposite sex. These findings are hypothesized to reflect (1) competitive conflict among those individuals in the group most similar to each other (members of the same age-sex class); (2) the protection and socialization of offspring by adult females; and (3) the modification of adolescent male aggressive expression by the selective interference of adult males. As a consequence of adult response to the agonistic behavior of adolescent males, maturing males (1) selectively target other older males, avoid aggression against females and immatures; (2) form alliances with other males; and (3) become progressively isolated from their matrilines.     

Getting ready for the winter: Timing and determinants of molt in an alpine ungulate

Because growth of new hairs entails energetic costs, individual condition and access to food should determine the timing of molt. Previous studies on the timing of molt in ungulates have mostly focused on the influence of age class and reproductive status, but the effects of body condition and environmental phenology have not been evaluated. Our goal was to assess how intrinsic traits and environmental conditions determine the timing of winter coat shedding in a mountain goat population monitored for 27 years. The date of molt completion followed a U shape with age, suggesting that senescence occurs in terms of the molting process in mountain goats. Juveniles of both sexes delayed molting in a similar fashion, but molt timing differed between sexes during adulthood. Males molted progressively earlier until reaching age when reproduction peaked, after which they started delaying molting again. Females reached earliest molt dates at age of first reproduction and then progressively delayed molt date. Lactating females molted 10 days later than barren females on average, but this only occurred in females in good condition. Thus, although it has been shown that reproduction delays molt in ungulates, our results indicate that body condition can override this effect. Overall, our results revealed that access to both extrinsic and intrinsic resources is one of the key mechanisms driving molting processes in a mammalian herbivore.     

STABILITY IN THE PROPORTION OF HARBOR SEALS HAULED OUT UNDER LOCALLY IDEAL CONDITIONS

We monitored the haul-out behavior of 68 radio-tagged harbor seals ( Phoca vitulina ) during the molt season at two Alaskan haul-out sites (Grand Island, August-September 1994; Nanvak Bay, August-September 2000). For each site, we created a statistical model of the proportion of seals hauled out as a function of date, time of day, tide, and weather covariates. Using these models, we identified the conditions that would result in the greatest proportion of seals hauled out. Although those "ideal conditions" differed between sites, the proportion of seals predicted to be hauled out under those conditions was very similar (81.3% for Grand Island and 85.7% for Nanvak Bay). The similar estimates for both sites suggest that haul-out proportions under locally ideal conditions may be constant between years and geographic regions, at least during the molt season.     

The phenology of molting,breeding and their overlap in central Amazonian birds

The energetically challenging periods of molting and breeding are usually temporally separated in temperate birds, but can occur simultaneously in tropical birds, a condition known as molt–breeding overlap. Here, we document great variation in the timing and duration of molting and breeding, and in the extent of molt–breeding overlap, among 87 species of understory passerines in central Amazonia. We analyzed molt and breeding from 26 871 birds captured over a 30‐yr period near Manaus, Brazil. Although most species typically bred during the late dry season (about October through January), many thamnophilids apparently bred year‐round, whereas a few other species from a variety of families bred mainly during the wet season (about January through May). Of all breeding birds with an active brood patch, 12.7% were simultaneously molting. Molt–breeding overlap was more frequently observed among suboscines (13.3%), especially thamnophilids (23.0%), than oscines (6.4%). Some families had <5% molt–breeding overlap frequency, including Tyrannidae (4.4%), Tityridae (0.0%), Pipridae (1.5%), Turdidae (0.0%), and Thraupidae (0.0%), indicating that not all tropical species exhibit molt–breeding overlap. Among 31 well‐sampled species (n ≥15 brood patches), variation in molt–breeding overlap frequency was positively correlated with each species’ average duration of flight feather replacement (range 98–301 d). We also measured feather growth rates of individual birds in nine species; in five of these, slower‐growing feathers increased with an individual's probability of having molt–breeding overlap. Among furnariids, molt–breeding overlap occurred either at the beginning or end of the molt cycle, suggesting that physiological mechanisms typically separate molting from breeding. Thamnophilids showed a much different pattern; molt–breeding overlap occurred at any stage of feather replacement, apparently not regulated to be independent of breeding. These results reveal substantial life‐history variation among Amazonian birds. Future work to resolve the physiological regulation of molting and breeding in tropical birds will greatly contribute to understanding these patterns and their relevance to avian diversity.     

Onset and duration of gray seal (Halichoerus grypus) molt in the Wadden Sea,and the role of environmental conditions

Surveys of gray seals (Halichoerus grypus) during the molt period, when they are abundant on land, can be used to monitor changes in population size, but accurate interpretation of results requires an understanding of the molt process and how it may vary between years. This study investigates variability in onset (start date) and duration of visible molt by gray seals in the Wadden Sea, and the influence of environmental conditions on the onset. Molt was monitored in nine captive seals and observed molt phases were applied to wild seals over seven annual molt periods between 2004 and 2010, monitored using aerial photography. The onset of visible molt varied significantly between years, for example it differed 28 d between 2008 and 2009. Model selection by AIC retained one environmental variable that correlated with molt onset; however, its effect was inconsistent within the molt season and did not explain some of the apparent observed annual variation. Hence, the main causes of interannual variability in the onset of molt remain unclear and warrant further study. Researchers should account for annual variability in the onset of molt when interpreting survey results based on molt counts.     

Juvenile southern elephant seals exhibit seasonal differences in energetic requirements and use of lipids and protein stores

Growing juvenile animals undergo many morphological, physiological, and behavioural changes that influence their energetic requirements, patterns of energy use, and ultimately, their survival and reproductive success. We examined changes in mass loss and body composition of juvenile southern elephant seals (1- and 2-yr-olds) during their two annual haul-outs. At the start and end of the midyear and molt haul-outs, we caught, weighed, and measured 41 and 14 seals, respectively. We measured blubber depth using ultrasound to estimate body composition (lean and adipose tissue mass). Using energy densities of the adipose and lean tissue, we calculated total, lean, and adipose mass changes and energy expenditure. While molting, juvenile seals used more energy than during the midyear, which is related to the increased use of lean tissue for hair and skin regeneration. The amount of energy used increases with mass as individuals mature. We found sexual differences in energy use where females retained greater fat reserves than males by utilizing more lean tissue. These differences are most likely related to haul-out function and behavior, growth, and earlier development of females toward sexual maturity.     

Timing and body condition of dichromatic Black Redstarts during autumn migration

Individual variation in postjuvenile molt in male Black Redstart is pronounced with about 90% of young males retaining female‐like coloration (cairei plumage type) and about 10% acquiring adult male‐like feathers (paradoxus plumage type). We examined whether autumn migration timing and body condition differed between individuals of the two plumage types. We used the data of 10,977 Black Redstarts captured during autumn at a ringing site in northern Switzerland where a protocol to record plumage types of captures has been applied since 1980. As cairei individuals cannot be distinguished from young females while sexing is comparatively easy for paradoxus individuals, the proportion of missing data on sex was likely to be higher for cairei individuals than for paradoxus individuals. We formally accounted for captures with unidentified sex using a Bayesian approach and conducted a simulation study to show that our approach was able to provide unbiased results even if the proportion of unsexed captures was high. Applying the method to the Black Redstart data, we found that the proportion of individuals with paradoxus plumage type increased from 7.6% in 1980 to 18.1% in 2013. Individuals with the paradoxus plumage type were on average 0.25 g heavier and had 0.62 mm longer third primaries than individuals with the cairei plumage type. However, we found no support for our expectation of later migration of paradoxus males compared to cairei individuals based on the assumption that paradoxus individuals should occupy autumn territories like adult males. Our results shed new light on the understudied timing of autumn migration in birds and are in line with available studies on Black Redstarts, suggesting a molt‐constraint that allows only young males in good body condition to molt into adult‐like plumages.     

Play in Harbour seals (Phoca vitulina)

Harbour seals in a breeding colony at Miquelon exhibited 13 distinct types of play behaviour, 80% of which was solitary locomotor play. Most play was displayed by yearlings and juveniles, though a significant amount of adult play occurred as well. Mothers and pups rarely played. Yearlings played socially as often as alone, but seals of other age classes played by themselves most often. Only social play resembled adult activities. It is suggested that the function of mammalian play has been obscured by its similarity to adult behaviour.     

Characterization of Australian fur seal vocalizations during the breeding season

The vocal repertoire, structure, and behavioral context of airborne vocalizations produced by Australian fur seals (Arctocephalus pusillus doriferus) are described using recordings made at a breeding colony on Kanowna Island, Bass Strait, Australia. The study identified six different call types: three produced by males (bark, guttural threat, and submissive call); five produced by females (bark, guttural threat, submissive call, growl, and pup attraction call) and the female attraction call produced by pups and yearlings. Vocalizations were compared according to age and sex classes. The overall structure and function of the pup attraction and female attraction call produced by females, yearlings, and pups, was similar. However, while similar in their overall appearance, certain call types have a lower fundamental frequency when compared with other fur seals. In addition, the male bark call alters in rate of production according to the context used, where calls are slower when males are stationary and advertising their territorial status and faster when males are involved in confrontations with other males or actively herding females. Further research is required to investigate changes in environmental conditions and their effects on shaping the call structure and communication in Australian fur seals.     

ABUNDANCE OF RINGED SEALS (PUSA HISPIDA) IN THE FJORDS OF SPITSBERGEN, SVALBARD, DURING THE PEAK MOLTING PERIOD

Ringed seal (Pusa hispida) abundance in Spitsbergen, Svalbard, was estimated during the peak molting period via aerial, digital photographic surveys. A total of 9,145 images, covering 41.7%–100% of the total fast‐ice cover (1,496 km²) of 18 different fjords and bays, were inspected for the presence of ringed seals. A total of 1,708 seals were counted, and when accounting for ice areas that were not covered by images, a total of 3,254 (95% CI: 3,071–3,449) ringed seals were estimated to be hauled out during the surveys. Extensive behavioral data from radio‐tagged ringed seals (collected in a companion study) from one of the highest density fjords during the molting period were used to create a model that predicts the proportion of seals hauled out on any given date, time of day, and under various meteorological conditions. Applying this model to the count data from each fjord, we estimated that a total of 7,585 (95% CI: 6,332–9,085) ringed seals were present in the surveyed area during the peak molting period. Data on interannual variability in ringed seal abundance suggested higher numbers of seals in Van Keulenfjorden in 2002 compared to 2003, while other fjords with very stable ice cover showed no statistical differences. Poor ice conditions in general in 2002 probably resulted in seals from a wide area coming to Van Keulenfjorden (a large fjord with stable ice in 2002). The total estimated number of ringed seals present in the study area at the time of the survey must be regarded as a population index, or at least a minimum estimate for the area, because it does not account for individuals leaving and arriving, which might account for a considerable number of animals. The same situation is likely the case for many other studies reporting aerial census data for ringed seals. To achieve accurate estimates of population sizes from aerial surveys, more extensive knowledge of ringed seal behavior will be required.