Age-dependent changes in sperm production, semen quality, and testicular volume in the black-footed ferret (Mustela nigripes)

The black-footed ferret (Mustela nigripes), which was extirpated from its native North American prairie habitat during the 1980s, is being reintroduced to the wild because of a successful captive-breeding program. To enhance propagation, the reproductive biology of this endangered species is being studied intensively. The typical life span of the black-footed ferret is approximately 7 yr. Female fecundity declines after 3 yr of age, but the influence of age on male reproduction is unknown. In this study, testis volume, seminal traits, sperm morphology, and serum testosterone were compared in 116 males from 1 to 7 yr of age living in captivity. Results demonstrated that testes volume during the peak breeding season was similar (P > 0.05) among males 1 to 5 yr of age, reduced (P < 0.05) among males 6 yr of age, and further reduced (P < 0.05) among males 7 yr of age. Motile sperm/ejaculate was similar in males 1 to 6 yr of age but diminished (P < 0.05) in those 7 yr of age. Males at 6 and 7 yr of age produced fewer (P < 0.05) structurally normal sperm than younger counterparts; however, serum testosterone concentrations were not reduced (P > 0.05) in older males. Histological comparison of testicular/epididymal tissue from 5- and 7-yr-old black-footed ferrets confirmed that the interval between these two ages may represent a transitional period to reproductive senescence. In summary, functional reproductive capacity of male black-footed ferrets exceeds that of females by at least 2 yr. Testes and seminal quality are indistinguishable among males 1 to 5 yr of age, with progressive reproductive aging occurring thereafter.     

Multiple mating strategies explain unexpected genetic mixing of New Zealand fur seals with two congenerics in a recently recolonized population

Human impacts on natural systems can cause local population extinctions, which may promote redistribution of taxa and secondary contact between divergent lineages. In mammalian populations that have mating systems shaped by polygyny and sexual selection, the potential for hybridization to ensue and persist depends on individual and demographic factors. At Macquarie Island, a recently formed fur seal population is comprised of both sexes of breeding Antarctic (Arctocephalus gazella) and subantarctic (A. tropicalis) fur seals, and an itinerant collection of male New Zealand fur seals (A. forsteri), presumed to be non-breeders due to their absence from principle breeding areas. The mating system of the three species is described as resource-defence polygyny: males defend beach territories containing breeding females for exclusive mating rights. A recent genetic study identified a high level of hybridization in the population (17-30%), unexpectedly involving all three species. This study examined the source of involvement in breeding by A. forsteri with respect to mating strategies operating in the population. Ninety-five (10%) pups born from 1992 to 2003 were genetically identified as New Zealand hybrids. Most resulted from reproduction within territories by New Zealand hybrids of both sexes, although some were conceived extra-territorially, indicating that males successfully utilize strategies other than territory holding to achieve paternities. Female reproductive status influenced mating partner and mating location, and females without pups were more likely to conceive extra-territorially and with A. forsteri males. This study illustrates an important consequence of low heterospecific discrimination in a sympatric population of long-lived mammals.     

BEHAVIORAL SIGNIFICANCE OF UNDERWATER VOCALIZATIONS OF CAPTIVE LEOPARD SEALS, HYDURGA LEPTONYX

Two groups of underwater vocalizations were identified in a three-year study of two captive leopard seals, Hydurga leptonyx (one female and one male at Taronga Zoo, Sydney). This was supplemented by recordings over three months from a male at Marineland, New Zealand. The sexual state of the seals at Taronga was deduced from serum hormonal concentrations: the female was considered to be in estrus at specific times during the breeding season. The seal at Marineland, New Zealand was assumed to be sexually mature on the basis of size and age. Of 12 different underwater sound types recorded, six were produced by the seals at Taronga Zoo during agonistic interactions (local calls) and were heard through most of the year. The other six sound types were produced by lone seals. These broadcast calls were produced by the female only when sexually receptive, and by the mature male during December and January, months believed to be the breeding season of wild leopard seals. We propose that underwater acoustic behavior is important in the mating system of this species, and that broadcast calls are used by mature females to advertise their sexual receptivity, and possibly by mature males in search of mates.     

ANALYSIS OF CORPORA LUTEA TO ESTIMATE REPRODUCTIVE CYCLES OF WILD HAWAIIAN MONK SEALS (MONACHUS SCHAUINSLANDI)

Ovaries from 14 female Hawaiian monk seals, O-24 yr of age, collected from the northwestern Hawaiian Islands were analyzed by gross and histological examination for the presence of corpora hemorrhagica (CH), lutea (CL), albicantia (CA), and dominant follicles. Seven seals, 5-24 yr of age, were mature females, and another seven seals, O-5 yr of age, were immature based on the presence or absence of CL and CA in the ovaries. Two 5-yr-old seals did not have CL and CA, but one J-yr-old and both 6-yr-old seals had CL or CA. In addition, the weight of the more active ovary increased at 5 yr of age, indicating that puberty in these female Hawaiian monk seals occurred about 5 yr of age. The total number of CL and CA was significantly correlated to the ovarian weight, but not age of the seals, indicating that visible CA of Hawaiian monk seals probably degenerate within a year. If an ovulation resulted in pregnancy, we assumed that the resulting CL from that pregnancy persisted throughout gestation and regressed approximately 2 yr after ovulation. However, the CL of pregnancy were not easily differentiated from cyclic CL that did not result in pregnancy. Four of seven mature seals were clearly polyestrous from the analyses of their ovaries and reproductive histories. The remaining three seals were pregnant in previous consecutive years, and we could not positively determine whether they were also polyestrous. The ovaries from Hawaiian monk seals had unusually large, rounded granular cells containing the aging pigment, lipofuscin. These cells were located between loose fibrous tissues in all regressing CL and CA but were not present in any CH.     

REPRODUCTION IN THE FEMALE SUBANTARCTIC FUR SEAL, ARCTOCEPHALUS TROPICALIS

The reproductive tracts of 89 female subantarctic fur seals, taken at Gough Island between November 1977 and October 1978, were examined. Females started ovulating at age 4 yr and all 6-yr-old females were sexually mature. They are mono-ovulatory, alternating between ovaries, and only single embryos were found. Females older than 13 yr ( n = 11) showed poor follicular development and some failed to ovulate. The gestation period (first recorded ovulation to first recorded birth) was 360 d, while delayed implantation (first recorded ovulation to first recorded implantation) lasted for 139 days. Follicle numbers in the functional ovary declined sharply after ovulation while the corpus luteum increased in size until at least 1 mo prior to parturition. The number of follicles in the contralateral ovary increased after midwinter (June/July), and the mean size of the largest follicles peaked prior to ovulation in December. The mean size of the largest follicles increased in both ovaries near implantation time, after reaching a low subsequent to, ovulation. The regressing corpus albicans, conspicuous for approximately 3 mo after parturition, could not be detected macroscopically within one year postpartum. Subantarctic fur seals at Gough Island have a distinct postreproductive class of older females. The pregnancy rate for all females ≥4 yr of age was 79%, and it was 84.5% for the sexually mature group of ≥6 yr of age, while the mean age at puberty was 4.80 yr.     

Pup growth of the New Zealand fur seal Arctocephalus forsteri on the Open Bay Islands, New Zealand

Growth of New Zealand fur seal pups was investigated at Taumaka, Open Bay Islands, New Zealand, from November 1974 to September 1976. Pups were weighed and curvilinear length, axillary girth and foreflipper length measured at about ages 55, 190, 235 and 290 days. Males are significantly heavier and larger than females at each age, wtih the exception of axillary girth at 235 days. Pups born during the austral summer of 1974–5 were smaller overall than were pups born during the following summer. This difference was so great that males aged 140 days in 1976 were larger and heavier than males aged 235 days in 1975. Circumstantial evidence suggests that the difference in growth rates of pups born during the two years may have been a consequence, either directly or indirectly, of environmental temperatures. Pups born during the warmer season (1974–5) had the slower growth.     

Sex and reproductive stage differences in the growth,metabolism, feed,fecal production,excretion and energy budget of the Amazon River prawn (Macrobrachium amazonicum)

The aim of this study was to evaluate differences in various physiological measures (growth, fecal production, feed intake, nitrogenous excretion, oxygen consumption, energy substrate used, and energy budget) among males, ovigerous females and non-ovigerous females of the freshwater prawn Macrobrachium amazonicum. This species exhibits pronounced sexual dimorphism and different male morphotypes and has the potential for use in aquaculture. Males and non-ovigerous females were studied for 30?days. Ovigerous females were studied for 10?days. Prawns were fed commercial prawn food, and all males were of the Translucent Claw (TC) morphotype. The results demonstrate physiological differences both between males and females and between females of different reproductive stages. Males had higher rates of ingestion, growth and oxygen consumption and less fecal loss than females. We postulate that in the absence of other morphotypes, TC males may exhibit increased growth rates. Males and females used protein as an energy substrate. Males channeled approximately 9% of their energy budget into growth, whereas non-ovigerous and ovigerous females channeled only 1.4?±?0.4 and 0.07?±?0.07%, respectively. Whereas males and non-ovigerous females channeled 9.0?±?9.74 and 61.8?±?3.0%, respectively, of the energy ingested into metabolism, ovigerous females channeled 97.7?±?4.7% into metabolism, likely due to the frequent beating of their pleopods, which oxygenates and cleans the eggs. As reported for marine prawns, males and non-ovigerous females of M. amazonicum lost approximately 5% of their ingested energy in exuviae. The physiological differences observed between the sexes and between females of different reproductive stages might reflect corresponding differences in patterns of activity, growth, and reproduction.     

AGE,GROWTH, AND REPRODUCTIVE PATTERNS OF DALL'S PORPOISE (PHOCOENOIDES DALLI) IN THE CENTRAL NORTH PACIFIC OCEAN

Life history parameters were estimated for Dall's porpoise, Phocoenoides dalli, from biological specimens collected in the western Aleutian Islands, during 1981–1987. Of 2,033 males and 3,566 females examined, reproductive data were available for 1,941 males and 1,906 females; ages were determined for 813 males and 1,297 females. Female sexual maturity was based on the presence of one or more corpus on either ovary; 845 were sexually immature and 1,061 were sexually mature. Two estimates of female average age at sexual maturity (ASM) were 3.8 and 4.4 yr; average length at sexual maturity (LSM) was 172 cm. Males were considered sexually mature when evidence of spermatogenesis was detected; 1,136 were sexually immature and 805 were sexually mature. Two estimates of male ASM were 4.5 and 5.0 yr; LSM was 179.7 cm. Physical maturity was assessed for 246 males and 446 females by examining the degree of fusion in thoracic vertebral epiphyses. For both sexes, the average age at physical maturity was 7.2 yr. Average length at physical maturity was 202.6 cm for males and 192.7 cm for females. Average lengths of physically mature males (x?= 198.1 cm, SE = 0.8566) and females (x?= 189.7 cm, SE = 0.4002) were significantly different(P < 0.0001). Early postnatal growth was rapid in both sexes. A secondary growth spurt in both mass and length was characteristic for both sexes; the increase in length preceded the mass increase by 1–2 yr. Average length at birth (LOB) was approximately 100 cm; birth mass averaged 11.3 kg (SE = 0.0772). By the time the umbilicus had healed (<2 mo), the average length and mass had increased to 114.1 cm and 23.8 kg, respectively. Gestation period based on projections using LOB was 12 mo, but this was considered an overestimate. Calving was modal, centered in early July; an annual reproductive interval was indicated. Among the sexually mature females, 120 were pregnant, 55 were pregnant and lactating, 321 were pregnant with colostrum, and 33 were “resting.” By 3 July (95% CI =x? 1 d), 50% of births had occurred, during each of the seven years sampled. The ovulation rate was estimated at 0.914 ovulations per average reproductive year. Enlarged follicles and recent ovulations were observed in postpartum females in late July.     

AGE, GROWTH, AND REPRODUCTION OF THE FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN

Abstract: In the coastal waters of western Kyushu, Japan, a total of 97 incidentally taken or stranded finless porpoises, Neophocaena phocaenoides , was collected for studying age, growth and reproduction. An additional 17 specimens from the Inland Sea were used for a comparison of life history. Mean neonatal body length was 78.2 cm. Both males and females grew to around 140 cm by 5 yr of age. The maximum body lengths of males and females in western Kyushu were 174.5 cm and 165.0 cm, respectively, which were smaller than those recorded in other Japanese waters. Females probably attain sexual maturity at ages of 6–9 yr and at body lengths of 135–145 cm. Males probably mature sexually at ages of 4–6 yr, at body lengths of 135–140 cm and at weight of testis of 40–150 g. The lack of females aged 5–6 yr and males aged 4–5 yr precluded firm conclusions on ages at sexual maturity. Parturition in western Kyushu was estimated to be prolonged from autumn to spring, whereas in the Inland Sea and Pacific waters it was restricted from spring to summer with a peak in April. These geographical differences and available information on distribution implies that the finless porpoises in western Kyushu constitute a local population.     

Lower reproductive success in hybrid fur seal males indicates fitness costs to hybridization

Hybridization among organisms can potentially contribute to the processes of evolution, but this depends on the fitness of hybrids relative to parental species. A small, recently formed population of fur seals on subantarctic Macquarie Island contains a high proportion of hybrids (17-30%) derived from combinations of three parental species: Antarctic, subantarctic and New Zealand fur seals. Mitochondrial control-region data (restriction fragment length polymorphisms) and nine microsatellites were used to determine the species composition of breeding adults, and hybrid male fitness was measured by comparing reproductive success (number of genetically inferred paternities) of hybrid and pure-species territory males over 6 years. No correlations were found between male reproductive success and three genetic measures of outbreeding, but this may be due to a relatively small number of dominant males analysed. Territory males fathered 63% of pups, but hybrid males had lower reproductive success than pure-species males despite having the same ability to hold territories. A greater proportion of females in hybrid male territories conceived extra-territorially than those in territories of pure-species males, and most (70 of 82) mated with conspecifics. This suggests the presence of reproductive isolating mechanisms that promote positive assortative mating and reduce the production of hybrid offspring. Although we found no evidence for male sterility in the population, mechanisms that reduce lifetime reproductive success may act to decrease the frequency of hybrids. Our study has identified a disadvantage of hybridization - reduced reproductive success of hybrid sons - that may be contributing to the persistence of pure lineages at Macquarie Island and the temporal decline in hybridization observed there.     

Age, growth and maturation of the deepwater squid Moroteuthis ingens (Cephalopoda: Onychoteuthidae) in New Zealand waters

 Individuals of the deepwater squid Moro- teuthis ingens were obtained from New Zealand waters at depths between 500 and 1452 m. Depth distribution suggested that there was an ontogenetic migration to deeper water by females in association with maturity. Males did not show any clear pattern in their depth distribution. Statolith increment analysis was also undertaken to obtain putative age and life span information. Based on statolith age estimates, M. ingens appears to be predominantly an annual species with the oldest individuals aged at 358 and 393 days for males and females respectively. The form of growth over the size range sampled was linear with females having a growth rate almost twice that of males. Back-calculated hatching dates revealed a peak in hatching in the austral winter between June and August. Maturation in males was more closely related to size rather than age whereas in females the pattern in ovary growth in relation to both mantle length and age was similar. Received: 23 January 1996/Accepted: 29 May 1996     

Ménage à trois on Macquarie Island: hybridization among three species of fur seal (Arctocephalus spp.) following historical population extinction

Human-induced changes to natural systems can cause major disturbances to fundamental ecological and population processes and result in local extinctions and secondary contacts between formerly isolated species. Extensive fur seal harvesting during the nineteenth century on Macquarie Island (subantarctic) resulted in extinction of the original population. Recolonization by three species has been slow and complex, characterized by the establishment of breeding groups of Antarctic and subantarctic fur seals (Arctocephalus gazella and Arctocephalus tropicalis) and presumed nonbreeding (itinerant) male New Zealand fur seals (Arctocephalus forsteri). One thousand and seven pups from eight annual cohorts (1992-2003) were analysed using mitochondrial control region data (RFLP) and 10 microsatellite loci to estimate species composition and hybridization. Antarctic fur seals predominated, but hybridization occurred between all three species (17-30% of all pups). Involvement of New Zealand fur seals was unexpected as females are absent and males are not observed to hold territories during the breeding season. The proportion of hybrids in the population has fallen over time, apparently owing to substantial influxes of pure Antarctic and subantarctic individuals and non-random mating. Over 50% of New Zealand hybrids and 43% of Antarctic-subantarctic hybrids were not F(1), which indicates some degree of hybrid reproductive success, and this may be underestimated: simulations showed that hybrids become virtually undetectable by the third generation of backcrossing. While human impacts seem to have driven novel hybridization in this population, the present 'time slices' analysis suggests some biological resistance to complete homogenization.     

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.     

Determinants of breeding dispersal in the sand lizard, Lacerta agilis, (Reptilia, Squamata)

We studied determinants of breeding dispersal (the distance that an animal shifts its mean home range co-ordinate between reproductive events) in an individually marked population of sand lizards (Lacerta agilis) in south west Sweden during 1987–1991. Female breeding dispersal was not determined by age, size, body condition, or number of partners, and females and males that dispersed further did not experience a higher mortality. However, females with a low reproductive output dispersed further than females that reproduced more successfully, and males that lost in bodily condition dispersed further than males that better maintained body condition. We also looked for relationships between age-differences and band-sharing similarity (DNA fingerprinting = DFP) in three categories of lizards — all females, all males, and males and females — to establish whether males would be likely to mate with close kin. Age-difference was strongly correlated with band-sharing in only one category, males and females. When males were older than females this relationship was not significant. However, when females were older than males, age-difference was strongly correlated with band-sharing. Furthermore, females that were old enough to be the mothers of the courting males shared significantly more bands with these males than did the younger females, including the females of the same age as the males. Although parental-specific DFP bands necessary for establishing paternity among our adult lizards were inaccessible to us, we suggest that our circumstantial evidence strongly suggests that some males mate with their mothers. Males that were more closely related with their neighbours also moved further when we controlled statistically for age and mating success. We suggest that by mating with many partners males not only increase their mating success, but also increase the probability of mating with females with ‘good genes’: mean heterozygosity of parents (as revealed by micro-satellites) were strongly correlated with offspring survival.     

Male-female affiliative relationships in naturally occurring ringtailed lemurs (Lemur catta) at the Beza-Mahafaly Reserve,Madagascar

Affiliative behavior between adult male and female ringtailed lemurs was examined as part of a project concerning male affiliation with conspecifics of all age/sex classes. Males in three social groups were studied over a 12 month period. Male-female preferred partnerships existed, and were variable according to reproductive season. Dominance rank, age, or tenure of the male did not appear to affect either the number of partnerships or frequency of affiliative behaviors that males had with females. However, males residing in groups with fewer males exhibited both higher frequencies of affiliative interactions with females and were nearest neighbors to females more often than males living in a group containing more males. Females were found to be responsible for proximity maintenance of male-female dyads in the majority of cases. Neither reproductive season nor seasonal availability of food resources strongly affected the frequency of affiliative interactions between males and females, it is proposed that an important aspect of successful group membership for male ringtailed lemurs relates to the development of social relationships with adult females. Males can benefit from such relationships in terms of greater centrality to the spatial core of the group, which can result in enhanced predator protection, greater opportunities for social contact, and potentially greater access to estrous females. © 1996 Wiley-Liss, Inc.     

Reproductive biology of the male Cape porcupine, Hystrix africaeaustralis

The reproductive tract of the male Cape porcupine is morphologically and histologically similar to that of New World hystricomorph rodents. Males are reproductively active throughout the year and attained sexual maturity (complete spermatogenesis) at an age of 8-18 months. Testes weight, epididymides weight and seminiferous tubule diameter attained asymptotic values at the age of 23-30 months. A tendency towards seasonality in the activity of accessory glands, preceded and accompanied by an increase in circulating plasma testosterone values, may be considered as a factor enforcing seasonal breeding in females. Testosterone concentrations in pubertal males were significantly higher than those recorded in sexually mature males.     

Serum haptoglobin concentrations in ringed seals (Pusa hispida) from Svalbard, Norway

Haptoglobin (Hp) levels were measured in blood serum from 185 apparently healthy ringed seals (Pusa hispida) from Svalbard (age range, 1-30 yr) collected during the spring seasons of 2002 through 2004. The Hp concentration was 0.26 +/- 0.02 g/l (mean +/- SE; range, 0.0-1.5 g/l). Maturity status, body condition index (CI), interactions between CI and maturity status, and sex and maturity status all had significant influences on Hp levels. Mature males had significantly higher Hp concentrations compared with mature females (0.30 +/- 0.03 vs. 0.17 +/- 0.01 g/l, F(1,16) = 14.9, P<0.01). No differences were found between Hp levels in immature male and female seals (0.33 +/- 0.06 g/l). The Hp levels increased significantly in immature seals when the CI decreased. Despite the fact that mature males had a significantly lower CI than mature females, no direct correlation was found between Hp concentration and CI among adults. The elevated Hp values found in mature males might be related to injuries inflicted among males while fighting during the mating season or to high stress levels related to mating competition. The Hp concentrations of ringed seals measured in this study are useful baseline data for development of a diagnostic tool for future monitoring of the general health of this and other ringed seal populations.     

Age distribution of lactating New Zealand sea lions: Interannual and intersite variation

The age distribution of 865 lactating New Zealand sea lions (NZSLs; Phocarctos hookeri ) was investigated over 3 yr (1999–2001) at two breeding colonies, Sandy Bay and Dundas Island, New Zealand. Lactating females were aged between 3 and 26 yr with a maximum observed age of 28 yr. The mean age of lactating females was 11.1 (SE = 0.16) yr. Age distributions peaked at ages 8 and 9 with a strong skew toward younger females, likely indicative of maximum recruitment into the breeding population by this age. There were significant intersite differences in age structure and also significant interannual differences in age distributions at Sandy Bay, but not at Dundas Island. Given that the two colonies are less than 10 km apart, have some interchange, and share foraging areas, these differences are surprising. However, the colony at Dundas Island is almost four times larger than Sandy Bay and may therefore be less sensitive to demographic or environmental stochasticity. That age distributions of NZSLs vary significantly over small temporal and spatial scales has important implications for the extrapolation of data from one site or year to the population level, and hence for their management and conservation.     

Precopulation Sexual Selection in Nysius huttoni White (Heteroptera: Lygaeidae) in Relation to Morphometric Traits

Nysius huttoni White is a polygamous bug, endemic to New Zealand, and an important pest of wheat and brassicas. This bug has a female-biased sexual size dimorphism but relative to body length, males have longer antennae, suggesting that the allometric scales of antennal–body relationships may be highly selective in sexual selection. Body weight and most morphometric traits measured have no effect on mating success of either sex. Males significantly preferred mating with females having thicker abdomens, more mature eggs, and longer ovipositors. This result suggests that males may select their mates on the basis of immediate reproductive benefit: fertilizing more eggs and ensuring better survival of these eggs. Males with large genital structures have mating advantages over those with small ones, suggesting that precopulation sexual selection in this species act on male genital traits rather than body weight and nonsexual traits. Finally, females significantly preferred males with greater slopes for the antennal-body relationship for mating. The allometry in the male antennal length may be an indicator of male reproductive fitness.     

Variance in male reproductive success and sexual size dimorphism in pinnipeds: testing an assumption of sexual selection theory

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