Life history of harbor porpoises (Phocoena phocoena) in Scottish (UK) waters

Life history parameters were determined for stranded and bycaught harbor porpoises (Phocoena phocoena) from Scottish (UK) waters (1992–2005). Fetal growth rate was 84.4 mm/mo and mean size at birth was 76.4 cm (range 65–88 cm). Males and females had a similar range of body lengths (65–170 cm and 66–173 cm, respectively), although asymptotic lengths were higher in females than males (approximately 158 cm and 147 cm, respectively). Nonpregnant females were significantly lighter, in relation to their length than males. Maximum estimated age was 20 yr for both sexes. Age at sexual maturity (ASM) was estimated as 4.35 yr in females and 5.00 yr in males. Conception occurred mainly in July and August although reproductively active males were recorded during April to July. Gestation lasted 10–11 mo, with calving mainly between May and July. Lactating females were recorded during June to November, while small calves with solid food in their stomachs were found mainly during February to May. Estimated pregnancy rate (0.34–0.40) is lower than recorded elsewhere, but is likely underestimated due to the prevalence of mature females of poor health status in the sample. Nevertheless, cetacean strandings can be an essential source of data on demographic parameters.     

Changes in the size,composition, and reproductive condition of wild marmoset groups (Callithrix jacchus jacchus) in north east Brazil

Five groups ofCallithrix jacchus jacchus were studied in the field in north east Brazil. Group size and composition were similar to that described for other callitrichids, but changes in group membership occurred much more frequently than previously reported. There was a 50% turnover in group membership in a six month period, and adult males changed groups particularly often. Most groups contained only one reproductively active female, but there was evidence that one group contained two females that were reproductively active simultaneously. Some groups had several adult females, and the role of reproductive female switched from one individual to another with time. Individual marmosets are faced with an unusually wide range of alternative life history strategies involving different combinations of location and reproductive condition. We argue that marmoset social organization is best studied at the level of the whole population within an area, rather than at the level of the individual group.     

Reproductive biology of bisexual and all-female populations of chaetodontid fishes from the southern Great Barrier Reef

Synopsis The reproductive biology of three species of chaetodonts from One Tree Reef (southern GBR) is described by analysis of gonads and population structure. Reproductive biology is related to age by a capture-markrecapture study of growth. For Chaetodon rainfordi there was a significant habitat effect. On the reef slope, females outnumbered males by 5.6: 1 and both sexes became reproductively active by the age of 2 years. In the lagoon, no males were found and females were reproductively inactive. For C. plebius, males were essentially missing from all samples and no reproductively active females were found. For Chelmon rostratus (1 :1 sex ratio) some males had mature testes but there was no evidence of female reproductive activity. This species is likely to be gonochoristic, but the reproductive mode of the other two species remains ambiguous.     

Reproductive traits of the acanthocephalan Neoechinorhynchus brentnickoli in the definitive host

The Acanthocephala constitute a group of helminth parasites that, as adults, infect all classes of vertebrates. Adults of Neoechinorhynchus brentnickoli are parasites of Dormitator latifrons, a commercially important fish species in Tres Palos Lagoon, Guerrero, Mexico. The aim of this study was to describe features of the reproductive biology of this acanthocephalan. Fish were collected from Laguna de Tres Palos during February 2012 to February 2013. The number of fish that were examined (n=688) ranged from 35 (June) to 70 (August) in each collection. The prevalence of infection was more than 90% during this period and mean abundance varied significantly from 32.3 worms per fish (July 2012) to 89.3 worms per fish (March 2012). Acanthocephalans were reproductively active during the whole year. The stomach was the region of the digestive tract with the smallest percentage of helminths, and females were more abundant than males in all sections of the intestine. Larger male and female worms were always located in the more posterior sections of the digestive tract. The mean length at which 50% of individuals reached sexual maturity was 2.9 mm for females and 2.3 mm for males. Relative fecundity increased with length in females.     

Reproductive seasonality in the Indian pygmy field mouse,Mus terricolor

The Indian pygmy field mouse, Mus terricolor, is a tiny, yet economically and ecologically important crop pest found throughout South-East Asia. There are no systematic reports exploring its reproductive physiology. We report the presence of distinct periods of annual reproductive activity and quiescence in M. terricolor. Body weight in males and females, relative weights of testis, epididymis and seminal vesicle in males, ovarian and uterine weight in females, gonadal histomorphic changes, testicular and ovarian cholesterol, sialic acid in epididymis, fructose in seminal vesicle, uterine protein content, melatonin in males and females, testosterone in males, estradiol, and progesterone in females were studied over a period of three years in both wild-caught and lab-acclimated mice. The number of Graafian follicles and corpora lutea, and plasma estradiol and progesterone, along with relative weights of ovary and uterus in females exhibited a peak in the months of October–January, compared to June. Based on histomorphic and hormonal status, the major reproductively active season is the winter (short-day breeding). There is a brief period of sub-maximal reproductive activity in April. M. terricolor is reproductively inactive in the summer, monsoons, and autumn. The results establish M. terricolor as a seasonal breeder in the field, with interesting implications for pest management.     

Reproduction elevates the corticosterone stress response in common fruit bats

Changes in reproductive state or the environment may affect the sensitivity of the hypothalamic-pituitary-andrenal (HPA) axis. However, little is known about the dynamics of the resulting corticosteroid stress response, in particular in tropical mammals. In this study, we address the modulation of corticosterone release in response to different reproductive conditions and seasonality in 326 free-living common fruit-eating bats (Artibeus jamaicensis) on Barro Colorado Island in Panama during dry and wet seasons. We present strong evidence that stress sensitivity is primarily modulated by reproductive condition. In reproductively active females, corticosterone increases were more rapid and reached higher levels, but also decreased significantly faster than in inactive females. The corticosterone response was weaker in reproducing males than in females and delayed compared to non-reproductive males. Testes volume in reproductively active males was negatively correlated with corticosterone concentrations. Our findings suggest differentiated dynamics in the corticosterone stress response between sexes, potentially reflecting conflicting ecological demands. In females, a strong acute corticosterone response may represent high stress- and risk-sensitivity that facilitates escape and thus helps to protect reproduction. In males, suppression during reproductive activity could reflect lowered stress sensitivity to avoid chronically elevated corticosterone levels in times of frequent aggressive and therefore costly inter-male encounters.     

Guppies control offspring size at birth in response to differences in population sex ratio

Females that invest adaptively in their offspring are predicted to channel more resources to the sex that will be at an advantage in the prevailing environmental conditions. Here, we report, for the first time, that female Trinidadian guppy, Poecilia reticulata, respond in reproductively distinct ways when faced with differences in operational sex ratio. We show that females assigned to a female‐biased sex ratio produce larger male offspring than females in an environment in which males predominate. Given the link between size at birth and fitness, and the marked reproductive skew in this species, larger male offspring are expected to have reproductive advantages in guppy populations with an excess of females. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 414–419.     

Bourgeois Males of the Peacock Blenny,Salaria pavo,Discriminate Female Mimics from Females?

In a Portuguese population of Salaria pavo, two types of reproductively active males occur: large bourgeois males that defend nests and have fully developed secondary sex characters (SSC) and small sneaker males that mimic the females’ morphology and behaviour to approach nests and parasitize fertilizations. These two alternative reproductive tactics are sequential, as sneakers develop into bourgeois males. We investigated whether bourgeois males were able to discriminate between sneakers and females of different sizes. In a laboratory experiment bourgeois males were sequentially presented with a female and a sneaker matched for size. Complementary field observations were conducted on the interactions between females and sneakers with bourgeois males. If bourgeois males discriminated females from sneakers, we predicted that they should direct more aggressive behaviours towards sneakers and more courtship acts towards females. In general, bourgeois males courted and attacked small females and sneakers equally. However, large sneakers were courted less and attacked more than large females. Larger sneakers, beginning to develop SSC, were attacked more and courted less by the bourgeois male than smaller sneakers, and larger females were attacked less and courted more than smaller females. These results strongly suggest that only small female‐mimicking males were able to deceive bourgeois males. In S. pavo, if the sneakers’ fertilization success correlates with their female‐mimicking ability, a fitness decrease with an increasing body size can be predicted.     

The effect of mating behaviour on progeny sex ratio of Mastrus ridens (Hymenoptera: Ichneumonidae), a biological control agent of codling moth

Mastrus ridens (Horstmann) (Hymenoptera: Ichneumonidae) was imported into quarantine as a potential biocontrol agent for codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae). Mating behaviour of the parasitoid and its effect on progeny sex ratio (as a proportion of males) were studied to help sustain the laboratory culture. Both females and males were reproductively active soon after emergence. Unmated females produced only male progeny, confirming males developed from unfertilized eggs. The proportion of males in a progeny was independent of the copulation period (24–40 s) of the parents. The progeny sex ratios from three parent ratios (f:m 2:1, 1:1 and 1:2) were not significantly different. Females effectively mated only once but males mated frequently in their lifetime. The progeny sex ratios from single females with a known single mating and possible multiple matings (through exposure to two males for 18 days) were not significantly different. However, when males copulated with five virgin females in sequence over a 2 h period, the fifth female produced more males than the preceding four, presumably due to sperm depletion. Results of this study provide data on progeny sex allocation of M. ridens that help to prevent the development of a male-biased sex ratio that could threaten the maintenance of the culture over time.     

Influence of Ecological and Social Factors on Body Mass of Wild Chimpanzees

The chimpanzees (Pan troglodytes schweinfurthii) of Gombe National Park, Tanzania, were weighed regularly over a period of 33 yr, resulting in 1286 measurements on 31 males and 26 females aged 2–43 yr. Female growth slowed at 10 yr and that of males at 13 yr. Median adult body mass is 39 kg for males and 31.3 kg for females. Body mass varied between years. Chimpanzees were heaviest during a period of frequent banana provisioning. They were also heavier when community range size was large and population density within the range was low. Chimpanzees were heavier in the wet than in the dry season and body mass tracked rainfall in the preceding mo except for May in which mass was anomalously low. Dominance rank is significantly correlated with body mass for females but not males. High-ranking individuals tended to maintain more stable mass. Variability in body mass was greater for young and old individuals than for prime adults.     

Size and protein content of accessory glands in adult male Caloptilia fraxinella in different physiological states

Reproductive diapause is a strategy employed by some insects to coordinate reproduction with the appropriate environmental conditions for mate location and offspring development. Male Caloptilia fraxinella Ely (Lepidoptera: Gracillariidae) eclose in July in reproductive diapause, and remain unmated until May of the next year, when they emerge from overwintering sites in a reproductively active state. The present study assesses characteristics of male sex accessory glands (SAG) throughout the adult life stage when males are reproductively active and in early and late reproductive diapause. Male SAG are longer and positively correlate with moth body size when males are reproductively active in the spring compared with males in reproductive diapause in the summer and autumn. Male SAG also contain significantly more protein during the period of reproductive activity than during reproductive diapause. Access to a carbohydrate nutrition source does not impact male SAG length or protein concentration when males are reproductively active in the spring. Treatment with a Juvenile Hormone analogue in the autumn, but not the summer, tends to increase the total protein concentration compared with that of untreated control moths.     

The prediapause copulation and its significance in the butterflyEurema hecabe

In the pierid butterflyEurema hecabe, which shows seasonal polymorphism (summer and autumn morphs) and overwinters at adult stage, whether or not the prediapause copulation may be of usual occurrence and reproductively functional was examined. From the counts of the spermatophores carried by the females, it is clear that the prediapause copulation characteristically occurs in reproductively inactive females of the autumn corph. From behavioral observations in the field, mating partners of those females are mostly males of the summer morph rather than from the autumn morph. In autumn, males of the summer morph remained abundant and searched for females on the larval food plants. Furthermore, they mated frequently with autumn morph females. Autumn morph males seemed to be sexually less active or inactive before hibernation. Microscopic examinations of the spermathecae were made in mated autumn-morph females collected before and after hibernation. The results indicate that sperm is passed by the males at autumnal copulation. The sperm may be stored in the female reproductive tract and utilized for fertilization in spring. This supposition is strongly supported by field data; that is, once-mated autumn-morph females laid fertilized eggs in spring. Finally, physiological basis of the prediapause copulation, its adaptive signficance and the behavioral advantage inE. hecabe are discussed from the viewpoint of seasonal adaptation.     

Life history of the Indo‐Pacific humpback dolphin in the Pearl River Estuary,southern China

We studied life history characteristics of the Hong Kong/Pearl River Estuary population of Indo‐Pacific humpback dolphins (Sousa chinensis), based on data from 120 specimens stranded between 1995 and 2009, 40 individuals biopsied at sea, and a long‐term (14+ yr) photo‐identification study. Ages were determined for 112 specimens by thin‐sectioning teeth and counting growth layer groups. Estimated length at birth was 101 cm. Longevity was at least 38 yr, and there was little difference in growth patterns of males and females. Growth was described by a Bayesian two‐phase Gompertz model; asymptotic length was reached at 249 cm. The tooth pulp cavity filled at an average of 18.5 yr of age. Physical maturity was reached at between 14 and 17 yr of age, apparently a few years after attainment of sexual maturity. Maximum lengths and weights of about 268 cm and 240 kg were attained. Females appear to lose all their spots by 30 yr, although males may retain some spotting throughout life. Calving occurred throughout the year, with a broad peak from March to June. Of 60 females monitored at sea for >14 yr of the study, none were documented to have more than three calves, suggestive of low reproductive output or low calf survival.     

Male and Female Reproductive Success in <Emphasis Type="Italic">Macaca sylvanus</Emphasis> in Gibraltar: No Evidence for Rank Dependence

The relationship between social rank and reproductive success is one of the key questions for understanding differences in primate social group structures. We determined the paternity of 18 infants in a social group of Barbary macaques (Macaca sylvanus) born over a period of 6 yr in the provisioned, free-ranging colony in Gibraltar. We successfully used 13 pairs of primers of variable microsatellite loci to amplify DNA from blood and hair samples and applied the computer programs CERVUS 2.0 and KINSHIP 1.3 to assign paternity to 13 candidate males. We collected data for 19 females that had given birth to 66 infants over a period of 7 yr. We used paternity analyses and female birth records to test the hypothesis that social rank is correlated with reproductive success. Results showed that numbers of paternities and maternities were equally distributed among all reproducing individuals in the social group regardless of rank. Subadult males reproduced as often as adult males. High-ranking females did not start to reproduce earlier than low-ranking females. Interestingly, there was a tendency toward a positive correlation between the ranks of mothers and the ranks of the corresponding fathers. It might be concluded either that a correlation between social rank and reproductive success is generally absent in Barbary macaques or that artificially favorable environmental conditions in Gibraltar preclude any correlation between social rank and reproductive success.     

Estrous asynchrony causes low birth rates in wild female chimpanzees

Estrous cycle asynchrony likely functions to elevate individual females' sexual attractiveness during female mate choice. Female chimpanzees show physiological estrus as anogenital swelling. Copulations are concentrated during the period of maximal tumescence, which is called the estrous period. A group of female chimpanzees in Mahale Mountains National Park, Tanzania, was shown to display asynchrony in both maximal tumescence and periovulatory periods. We tested the hypothesis that females establish asynchronous maximal tumescence or periovulatory periods with respect to other females to increase copulation frequency and birth opportunities (Hypothesis 1). We analyzed differences in birth rates between four asynchronous years and five nonasynchronous years. Counter to Hypothesis 1, females in periovulatory periods during asynchronous years showed significantly lower birth rates than those in nonasynchronous years. In addition, periovulatory females copulated more frequently on days on which no other female in a periovulatory period was present. These results suggest that birth rates tend to decrease when females experience nonoverlapping ovulation cycles, although copulation frequency is high. Such a decrease in the birth rate may have resulted from the cost associated with multiple copulations. We tested two other hypotheses: paternity confusion (Hypothesis 2) and sperm competition (Hypothesis 3). Both of these hypotheses were partially supported. The highest‐ranking male most effectively monopolized access to receptive females when relatively few other males and receptive females from the party (or subgroup) were present. The viability of Hypotheses 2 and 3 requires that dominant males are able to hinder a female from mating with other males. Given that the male‐biased operational sex ratio created by female asynchrony is likely to reduce the efficiency of mate guarding by dominant males, an asynchronous female may gain a fitness benefit by increasing the probability of mating with at least one male who produces superior sperm. Am. J. Primatol. 73:180–188, 2011. © 2010 Wiley‐Liss, Inc.     

Evidence for seasonal variation in aggressive behaviour by Macaca mulatta

Observations were made on the Macaca mulatta colony on the island of Cayo Santiago over a period that included two reproductive cycles. The frequency of aggressive behaviour was found to fluctuate cyclically as a function of the colony's reproductive state. Males were wounded and died significantly more frequently during the mating season than at any other time of year. Females were wounded about as often during the mating season as during the birth season, and more died during the birth season than during the mating season, although not significantly so. There was no significant difference between sexes in age at death, nor was there a significant departure from expectation of number of deaths per age class. However, mortality among the reproductively mature males was greater than among mature females. It was suggested that differential injury and mortality rates among adult males might be an indirect result of high levels of androgens which could conceivably alter threshold levels for stimuli initiating severe aggressive interactions.     

Reproduction of the large fruit-eating bat Artibeus lituratus (Chiroptera: Phyllostomidae) in a Brazilian Atlantic forest area

In this study we investigated the male testicular activity and the reproductive condition of females in relation to their external reproductive characteristics (pregnant, lactating, post-lactating) in the phyllostomid bat Artibeus lituratus (Olfers, 1818). Five hundred and twenty six individuals were examined (197 males and 329 females) in the period December 2001 to May 2003. Throughout the study most males displayed large scrotal testes. Thirty-three males were randomly selected for histological examination at various times throughout the year and were found to have spermatogenic testes. The reproductive characteristics of the females indicated that they were reproductively active mainly during the wet season. Pregnancy occurs at the end of the dry season and parturition in the wet season. Most individuals captured after this season, mainly the females, were sexually immature. Our results suggest a seasonal monoestrous reproductive pattern for the species; however, adult males being fertile throughout the year could suggest polyoestry. Seasonal polyoestry is a possibility. There was, however, no evidence that females had more than one pregnancy per year.     

Seasonal breeding in rhesus monkeys: Influence of the behavioral environment

The accepted model of breeding seasonality in rhesus monkeys states that females become reproductively active in response to an environmental cue and that males become sexually active in response to ovulating females. This model must be modified to include direct responses of the male to the physical environment, endocrine responses of males to sexual activity, and responses of the female to the sexual activation of fellow group members. The complex set of social stimuli that influences the breeding readiness of both sexes may serve to delimit more precisely the annual periods of conception and birth than would be the case if each individual responded only to the changing physical environment.     

Reproductive behavior and the maintenance of all-female Poecilia

Synopsis There are four members involved in the breeding complexes of poeciliid fishes found in the freshwaters of northeastern Mexico: males and females of a bisexual species, and diploid and triploid unisexuals. Both unisexuals reproduce by gynogenesis, i.e., an asexual type of reproduction where the sperm triggers egg development but the male genome is excluded to produce clonal offspring. The three types of females are closely related, which suggests that they are potential competitors since all three require the service of the same males. The potential for competition is compounded by a highly skewed sex ratio in favor of females. On the average the unisexuals comprise about 30% of the Poecilia females. This high frequency coupled with a close genetic relatedness to their bisexual hosts, raises the question of how the unisexuals are maintained in nature.Other investigators who work with bisexual/unisexual complexes in the related genus, Poeciliopsis, have postulated that male dominance hierarchies are responsible for restricting the access of subordinate males to their conspecific females. Consequently, these subordinate males mate with unisexual females. The current report tests whether or not this hypothesis applies to bisexual/unisexual complexes of Poecilia.We have found that linear dominance hierarchies appear to function in the defense of home ranges and do not restrict access of males to females. Dominant males exhibit less mating activity than subordinate males towards females. Previous reports showed that males are reproductively competent throughout the year, whereas females show striking asynchrony in their reproductive readiness. Such asynchrony limits the proportion of receptive females at any one time. Consequently, there are more males ready to mate than there are females receptive to their mating attempts. This may lead to mating frenzies. We postulate that these indiscriminate matings maintain the fertility of both unisexuals. When the relative reproductive outputs of adult females are compared, both unisexuals appear as fit as their bisexual congeners.     

A new interpretation of the social organization and mating system of the Callitrichidae

Tamarins and marmosets are usually described as monogamous, or as living in extended family groups. Field research on a variety of callitrichid species shows, however, that immigration and emigration by adults are common and that groups are likely to be composed largely of unrelated adults of both sexes. Despite the number of adult females present in a group, only a single female is usually reproductively active. This female may mate with more than one male. Care for the young is provided by all group members but principally by adult males. This generally is referred to as a “communal breeding system. ” However, a vertebrate social system in which more than two reproductively active adults participate in infant care is rare and has otherwise been reported only in a small number of avian and canid species. Wild callitrichid groups virtually always include helpers, but the number of adults of each sex is highly variable. We propose that the Callitrichidae tend to live in small multimalemultifemale groups, communally rear the young of one female, and exhibit a mating pattern characterized by female promiscuity but a breeding system that is functionally polyandrous. There is a significant correlation between the number of males and a group and the total number of surviving young. The possible adaptive advantages of this social organization are discussed. An erratum to this article is available at .