Allonursing in captive belugas (Delphinapterus leucas)

This study describes allonursing (females nursing offspring that are not their own) in captive belugas (Delphinapterus leucas). In addition to the calf's mother, two females that were not pregnant or nursing at the time of the calf's birth spontaneously lactated and nursed the male calf intermittently throughout 34 months of his life at the Vancouver Aquarium Marine Science Center. These observations suggest that allonursing may also take place in their wild counterparts and add to existing evidence of alloparental care in this species. Alloparental care, the care of nonoffspring, has been observed in every major mammalian taxon; the protection of calves through alloparental care may be a strong evolutionary benefit. Zoo Biol 29:633–637, 2010. © 2010 Wiley‐Liss, Inc.     

Joint estimation of survival and breeding probability in female dolphins and calves with uncertainty in state assignment

While the population growth rate in long‐lived species is highly sensitive to adult survival, reproduction can also significantly drive population dynamics. Reproductive parameters can be challenging to estimate as breeders and nonbreeders may vary in resighting probability and reproductive status may be difficult to assess. We extended capture–recapture (CR) models previously fitted for data on other long‐lived marine mammals to estimate demographic parameters while accounting for detection heterogeneity between individuals and state uncertainty regarding reproductive status. We applied this model to data on 106 adult female bottlenose dolphins observed over 13 years. The detection probability differed depending on breeding status. Concerning state uncertainty, offspring were not always sighted with their mother, and older calves were easier to detect than young‐of‐the‐year (YOY), respectively, 0.79 (95% CI 0.59–0.90) and 0.58 (95% CI 0.46–0.68). This possibly led to inaccurate reproductive status assignment of females. Adult female survival probability was high (0.97 CI 95% 0.96–0.98) and did not differ according to breeding status. Young‐of‐the‐year and 1‐year‐old calves had a significantly higher survival rate than 2‐year‐old (respectively, 0.66 CI 95% 0.50–0.78 and 0.45 CI 95% 0.29–0.61). This reduced survival is probably related to weaning, a period during which young are exposed to more risks since they lose protection and feeding from the mother. The probability of having a new YOY was high for breeding females that had raised a calf to the age of 3 or lost a 2‐year‐old calf (0.71, CI 95% 0.45–0.88). Yet, this probability was much lower for nonbreeding females and breeding females that had lost a YOY or a 1‐year‐old calf (0.33, 95% CI 0.26–0.42). The multievent CR framework we used is highly flexible and could be easily modified for other study questions or taxa (marine or terrestrial) aimed at modeling reproductive parameters.     

Corticosterone Levels Correlate With Alloparental Care in a Sex‐Dependent Manner in African Striped Mice,Rhabdomys pumilio

Alloparental care of non‐breeders is the main characteristic of cooperatively breeding species. While many studies have contributed to the understanding of the evolutionary reasons why individuals provide care to young that are not their own offspring, the variables influencing and causing alloparental care are less understood. We tested in African striped mice (Rhabdomys pumilio) whether age, sex, testosterone and corticosterone were correlated with alloparental care of non‐breeding helpers. We studied 11 family groups under controlled conditions in the laboratory, each with two juvenile and two adult helpers, one being male and one being female in each age category. We predicted male helpers to show more alloparental care than female helpers, as males are the dispersing sex and might thus have to pay for staying. We also expected adult helpers to show more alloparental care than juvenile helpers and both corticosterone and testosterone to correlate negatively with alloparental care. We found high levels of alloparental care in non‐breeding striped mice, which spent a significant amount of time in the nest, huddling and licking pups. There was neither a difference between the sexes nor between age categories (although both factors were significant in interaction terms), indicating either low costs and/or high benefits of alloparental care. Mothers showed significantly more care than helpers, and fathers showed similar levels of parental care as mothers but not significantly more than helpers. Although testosterone levels differed significantly between helpers of different age and sex, with adult male helpers showing the highest levels, we did not find any relationships between testosterone and the amount of alloparental care. Corticosterone levels were negatively correlated with alloparental care, and these effects were modulated by the sex and the age of helpers. In females, less alloparental care was shown with increasing corticosterone levels, while in males, the relationship was positive. Also, younger individuals with lower corticosterone levels showed more alloparental care than older individuals with low corticosterone levels. In sum, alloparental care is well developed in male and female non‐breeding helpers of striped mice, both in adult and juvenile helpers, but independently of testosterone, with corticosterone showing an age‐ and sex‐specific relationship with alloparental care.     

First evidence for adoption in California sea lions

Demographic parameters such as birth and death rates determine the persistence of populations. Understanding the mechanisms that influence these rates is essential to developing effective management strategies. Alloparental behavior, or the care of non-filial young, has been documented in many species and has been shown to influence offspring survival. However, the role of alloparental behavior in maintaining population viability has not been previously studied. Here, we provide the first evidence for adoption in California sea lions and show that adoption potentially works to maintain a high survival rate of young and may ultimately contribute to population persistence. Alloparental behavior should have a positive effect on the population growth rate when the sum of the effects on fitness for the alloparent and beneficiary is positive.     

Reproduction,birth seasonality,and calf survival of bottlenose dolphins in Doubtful Sound,New Zealand

Understanding the reproductive parameters of very small or declining populations is of clear importance to conservation. From 1995 to 2011 we recorded calf production (n = 71) and calf survival for 27 breeding females in the bottlenose dolphin (Tursiops truncatus) population in Doubtful Sound, New Zealand; a population with a recent history of declining abundance. Overall, 67% of calves survived their first year, and 40% survived to 3 yr (or are 2 yr old and still alive). Most calves that died in the first year died in their first month (87%). Multiparous mothers (n = 18) showed high variation in calf survival. The most successful six had all but one of their 20 calves (95%) survive to 1 yr. Fourteen of the 20 (70%) survived to 3 yr, and another four are still alive and are 1 or 2 yr old. In contrast, the least successful seven mothers produced a similar number of calves (21), eight of which (38%) survived to 1 yr, and none to 3 yr. Here we describe calving seasonality and calf survival, observed over 16 yr, and show that large variation in reproductive success of individual females is an example of extreme demographic stochasticity in this small, endangered population.     

Grandmotherly care: a case study in Indian free-ranging dogs

Parental care is an essential component in the life history of mammals. In group-living species, care can be provided by adults other than the parents, and such care is termed alloparental care. Alloparental care is known in a wide spectrum of species, from insects to humans. Most canids that live in stable packs demonstrate cooperative breeding, where subordinates provide care to the offspring of the dominants, without reproducing themselves. Free-ranging dogs in India have a dynamic social system and, unlike their cooperatively breeding ancestors, the grey wolves, all adults in a dog group have equal mating opportunities. This at times leads to the birth of multiple litters within an existing dog group. In this paper, we report the first field observations of alloparental care made on a dog group where a bitch provided care to her grandpups, through interactions other than suckling. The allomaternal care acted as a supplement to the care provided by the mother, and was thus beneficial to the pups.     

Comparison of reproductive parameters for populations of eastern North Pacific common dolphins: Delphinus capensis and D. delphis

Reproductive parameters were estimated and compared for eastern North Pacific populations of common dolphins using specimen and photogrammetric data. Age and length data for Delphinus capensis and D. delphis specimens recovered as bycatch or strandings were used to estimate the postnatal growth rates needed to estimate age for calves measured in aerial photographs. Bayesian methods propagated uncertainty among models and revealed that the 2009 cohort of calves had birth dates centered on 6 March 2009 for D. capensis and 12 December 2008 for D. delphis. The evidence for discrete calving seasons suggests a mechanism of reproductive isolation has evolved between species. Photogrammetric data and Bayesian methods were also used to estimate the average length at which calves swim independently: 145.1 cm (≈ 11.1 mo) in D. capensis and 140.1 cm (≈ 14.0 mo) in D. delphis, and the proportion of calves (calves/dolphins counted): 0.045 in D. capensis and 0.069 in D. delphis. The latter parameter was converted to an index of calf production (calf/female dolphin) that was >50% lower than pregnancy rates suggesting few births occurred during the study year. Comparisons of regional differences in calf production suggest variability in habitat use patterns within the study area.     

Genetic evidence for prevalence of alloparental care in a socially monogamous biparental cichlid fish,Perissodus microlepis,from Lake Tanganyika supports the “selfish shepherd effect” hypothesis

Alloparental care – care for unrelated young – is rare in animals, and its ecological or evolutionary advantages or, alternative maladaptive nature, remain unclear. We investigate alloparental care in the socially monogamous cichlid fish Perissodus microlepis from Lake Tanganyika that exhibits bi‐parental care. In a genetic parentage analysis, we discovered a surprisingly high percentage of alloparental care represented by brood mixing, extra‐pair paternity and extra‐pair maternity in all broods that we investigated. The percentage of nondescendant juveniles of other parents, i.e., brood mixing, ranged from 5% to 57% (mean = 28%). The distribution of genetic parentage also suggests that this socially monogamous species has, in fact, polygamous mating system. The prevalence of genetically mixed broods can be best explained by two, not mutually exclusive hypotheses on farming‐out and fostering behaviors. In the majority of broods, the sizes of the parents’ own (descendant) offspring were significantly larger than those of the adopted (nondescendant) juveniles, supporting the ‘selfish shepherd effect’ hypothesis, i.e., that foster parents preferentially accept unrelated “smaller or not larger” young since this would tend to lower the predation risks for their own larger offspring. There was also a tendency for larger parents particularly mothers, more so than smaller parents, to care predominantly for their own offspring. Larger parents might be better at defending against cuckoldry and having foreign young dumped into their broods through farming‐out behavior. This result might argue for maladaptive effects of allopatric care for the foster parents that only larger and possibly more experienced pairs can guard against. It needs to be determined why, apparently, the ability to recognize one's own young has not evolved in this species.     

Abundance estimation of gray whale (Eschrichtius robustus) calves from shore‐based surveys undertaken near Ensenada,Baja California,Mexico, 2004–2006

Gray whale calf abundance was estimated from shore‐based surveys near Ensenada, Baja California, during their northbound migration. Over the course of 129 effort‐days (756.5 observation hours), 162 calves were counted, comprising 42, 41, and 79 calves in 2004, 2005, and 2006, respectively. To estimate the number of undetected calves during the observation periods in 2006, detection probabilities were estimated by simultaneous and independent counts using a Huggins model. The detection probabilities ranged from 0.655 to 0.997. The number of calves estimated during effort periods were divided by their estimated detection probabilities, while the total number of calves were estimated by fitting a generalized additive model (GAM) to the passage rate (whales/h) and effort (time) data. The final gray whale calf abundance estimates were 451 (95% CI = 430, 513), 253 (95% CI= 245, 308), and 442 (95% CI = 396, 510) calves for 2004, 2005, and 2006, respectively. The estimates were lower than those reported for Piedras Blancas, California, during the same years, with one possible reason being that an important number of cow/calf pairs migrate too far from shore (>10 km) to be detected from the observation site used in this research.     

How does social behavior differ among sperm whale clans?

When individuals primarily associate with and learn from those who behave similarly, society and culture become closely tied. Sperm whales (Physeter macrocephalus) exhibit multilevel social structure, the levels of which are differentiated in part by characteristic cultural behaviors. Sperm whales are organized into sympatric clans, with distinctive vocal repertoires that are socially learned. Other behaviors, such as movement patterns and foraging, also differ among clans. Here we ask whether the clan partition also includes divergences in social behavior. Off the Galápagos Islands, members of two clans differed consistently in diving synchrony, heterogeneity, and temporal stability of social relationships. While number of associates (indicated by social unit, group, and cluster sizes) were similar between clans, Regular clan members dived more synchronously and had more homogeneous relationships than the Plus‐One clan members. Plus‐One social units had generally longer associations than those of the Regular clan. Differences in surface‐time coordination and quality of social relationships are likely byproducts of the clan segregation, which could affect alloparental care giving, therefore scaling up to differential calf survival rates between clans. This new dimension of behavioral divergence between sperm whale clans indicates that sympatric, socio‐cultural entities of nonhumans can also display characteristic social behavior.     

Effects of inbreeding on fitness‐related traits in a small isolated moose population

Inbreeding can affect fitness‐related traits at different life history stages and may interact with environmental variation to induce even larger effects. We used genetic parentage assignment based on 22 microsatellite loci to determine a 25 year long pedigree for a newly established island population of moose with 20–40 reproducing individuals annually. We used the pedigree to calculate individual inbreeding coefficients and examined for effects of individual inbreeding (f) and heterozygosity on fitness‐related traits. We found negative effects of f on birth date, calf body mass and twinning rate. The relationship between f and calf body mass and twinning rate were found to be separate but weaker after accounting for birth date. We found no support for an inbreeding effect on the age‐specific lifetime reproductive success of females. The influence of f on birth date was related to climatic conditions during the spring prior to birth, indicating that calves with a low f were born earlier after a cold spring than calves with high f. In years with a warm spring, calf f did not affect birth date. The results suggest that severe inbreeding in moose has both indirect effects on fitness through delayed birth and lower juvenile body mass, as well as separate direct effects, as there still was a significant relationship between f and twinning rate after accounting for birth date and body mass as calf. Consequently, severe inbreeding as found in the study population may have consequences for population growth and extinction risk.     

Neonatal Milestones,Behavior and Growth Rate of Sumatran Rhinoceros (Dicerorhinus sumatrensis) Calves Born and Bred in Captivity

The birth of Sumatran rhino calves at the Cincinnati Zoo and Botanical Garden offered a unique opportunity to study early development and cow–calf behavior in this elusive, critically endangered species. Study goals were to: (1) record developmental milestones of newborn calves; (2) characterize cow and calf behavior during the first year following birth; (3) compare trends in the behavioral development of a male vs. female calf; and (4) record weight gain and footprint size throughout the first year. In addition to recording eight neonatal milestones, more than 450 hr of behavioral data were collected on each of the two calves (one male and one female) and their dam during the first 12 months of life. Neonatal milestones were achieved within 24 hr of birth with the exception of first defecation, which occurred at 16–18 days. Although nursing bouts decreased slightly in the second half of the year (from once every 90 min to once every 2 hr), they continued to occur frequently throughout the day and night. Therefore, calves grew rapidly from approximately 33 kg at birth to 400 kg at 12 months. Average daily weight gain for the first week was approximately 2.0 kg, whereas average daily weight gain for the remaining 12 months was slight (<1 kg) and did not differ between calves. Eating and resting occupied 70–80% of the Sumatran rhino cow and calves' time and no gender biases in either maternal investment or developmental parameters were noted. Finally, footprint measurements proved valuable for estimating calf age. Zoo Biol 31:546‐560, 2012. © 2011 Wiley Periodicals, Inc.     

Resightings of humpback whales in Hawaiian waters over spans of 10–32 years: Site fidelity,sex ratios,calving rates,female demographics,and the dynamics of social and behavioral roles of individuals

From a database of approximately 5,000 Hawaiian humpback whales identified photographically between 1976 and 2010, we extracted 71 males and 39 females having resighting spans of 10 or more years, from first to most recent sighting. Findings included: (1) the male‐biased sex ratio was like that found in breeding grounds worldwide; (2) the mean span for males of 20.7 yr (maximum = 32 yr) did not differ significantly from the mean of 19.8 yr (maximum = 29 yr) for females, but males were seen in significantly more years during their spans than were females; (3) the mean number of females seen with and without calf across 11 three‐year intervals from 1977 to 2009 did not differ significantly; (4) the calving rate for the 39 females was 0.48 and seven females produced two to eight calves over spans of 22–26 yr; (5) females attracted significantly more escorts in years without calf than in years with calf; (6) individuals showed great diversity in the social units they occupied over their sighting spans, but with the most frequently observed unit for both sexes being the trio of mother, calf, and escort. Males were also observed frequently in competitive groups centered about a female without calf.     

Alloparental behavior in a captive group of spider monkeys (Ateles geoffroyi) at the Auckland zoo

I studied alloparental behavior in a captive group of spider monkeys at the Auckland Zoo using seven infants as focal subjects and assessed the effects of age, sex, and reproductive status of alloparents on patterns of infant-other interaction. Adult males initiated interactions with infants most often, followed by adult females. Immature individuals interacted with infants infrequently. Infants themselves initiated contact with adult males more often than with other members of the group. Alloparental behavior in spider monkeys differs from that in most other species in that the infant is an active rather than a passive participant in alloparental interactions. I discuss the patterns of infant-other interaction in relation to the social structure and dispersal patterns of Ateles.     

Parental behavior and infant development in ruffed lemurs (Varecia variegata) in a northeast Madagascar rain forest

Parental behavior and infant development of black and white ruffed lemurs (Varecia variegata) were studied on Nosy Mangabe Island in northeast Madagascar. Ruffed lemur females produced twins, prepared nests for neonates in the trees, transported infants by mouth, and parked them in the trees. During two consecutive birth seasons, the average birth rate for nine females was 0.58. Two females reproduced in one social group. Lactating females spent most of their time resting with their infants or foraging for food. Infants developed rapidly and were fully mobile by 3–4 months. No female reproduced successfully in 2 consecutive years. In 1988, infant mortality within 3 months of birth was very high (64%). Accidental falls may have been one major cause. Adults of both sexes, including a reproductive female, exhibited alloparental behavior such as guarding infants and nonmaternal nursing. Alloparental care may increase the likelihood of infant survival. Some of these observations are not compatible with the idea that ruffed lemurs live in small pair-bonded groups, as other researchers have suggested.     

Variations in age‐ and sex‐specific survival rates help explain population trend in a discrete marine mammal population

Understanding the drivers underlying fluctuations in the size of animal populations is central to ecology, conservation biology, and wildlife management. Reliable estimates of survival probabilities are key to population viability assessments, and patterns of variation in survival can help inferring the causal factors behind detected changes in population size. We investigated whether variation in age‐ and sex‐specific survival probabilities could help explain the increasing trend in population size detected in a small, discrete population of bottlenose dolphins Tursiops truncatus off the east coast of Scotland. To estimate annual survival probabilities, we applied capture–recapture models to photoidentification data collected from 1989 to 2015. We used robust design models accounting for temporary emigration to estimate juvenile and adult survival, multistate models to estimate sex‐specific survival, and age models to estimate calf survival. We found strong support for an increase in juvenile/adult annual survival from 93.1% to 96.0% over the study period, most likely caused by a change in juvenile survival. Examination of sex‐specific variation showed weaker support for this trend being a result of increasing female survival, which was overall higher than for males and animals of unknown sex. Calf survival was lower in the first than second year; a bias in estimating third‐year survival will likely exist in similar studies. There was some support first‐born calf survival being lower than for calves born subsequently. Coastal marine mammal populations are subject to the impacts of environmental change, increasing anthropogenic disturbance and the effects of management measures. Survival estimates are essential to improve our understanding of population dynamics and help predict how future pressures may impact populations, but obtaining robust information on the life history of long‐lived species is challenging. Our study illustrates how knowledge of survival can be increased by applying a robust analytical framework to photoidentification data.     

Does disappearance mean extirpation? The case of right whales off Namibia

Right whales off Namibia were severely depleted by early 19th century whaling, and rarely featured in modern whaling catches in the 1920s. Aerial surveys of the Namibian coastline from 1978 and onwards revealed increasing numbers of right whales, but few cow‐calf pairs. Aerial surveys off South Africa since 2009 showed a major decline in the availability of animals without calves. Twenty individual matches were made between 94 whales photographed off Namibia/Northern Cape in 2003–2012 and 1,677 photographed off South Africa in 1979–2012. Eight were adult females that calved in South African waters, but only one was also seen with a calf off Namibia. Twelve out of 13 individuals off Namibia with distinctive dorsal pigmentation were first seen as calves off South Africa. These results strongly indicate connectivity between the two regions, while the presence off Namibia of three adult females from the South African population in the season in which they are believed to conceive suggests that there is unlikely to be any genetic differentiation between the two areas. We conclude that the reappearance of right whales off Namibia represents range expansion from South Africa rather than the survival of a few remnants of an originally separate stock.     

Moose calf mortality in central Ontario,Canada

Although some populations remain stable, moose (Alces alces) density and distribution have been declining in many areas along the southern edge of their North American distribution. During 2006–2009, we deployed 99 vaginal implant transmitters (VITs) in 86 adult female moose in central Ontario, Canada to assist in locating and radiocollaring neonatal moose calves. We monitored radiocollared calves to estimate calf survival and assess the relative importance of specific causes of death. Calves in the western portion of our study area (WMU49) were exposed to a 6-day general hunting season, whereas calves in the eastern portion of our study area (Algonquin Provincial Park [APP]) were not exposed to hunting. Annual survival for 87 collared calves was greater in the protected area than the harvested area (72.4 ± 6.8% and 55.8 ± 8.3%, respectively) and averaged 63.7 ± 7.1% overall. Predation by wolves (Canis sp.) and American black bears (Ursus americanus) was the dominant cause of death but occurred predominately in APP, whereas other natural mortality agents were 4× more common in WMU49. Only 16% of the collared calves in WMU49 were harvested each year despite a high proportion (approx. 50%) of accessible, public land. Most natural mortality occurred prior to the autumn hunting season such that reductions in natural mortality had little potential to compensate for calf harvest. Overall, calf survival in our study area was moderate to high and our findings suggest predator control or further restrictions of calf hunting in this area is not justified. © The Wildlife Society, 2013