Characterization of basal seminal traits and reproductive endocrine profiles in North American river otters and Asian small-clawed otters

Current knowledge in the biology of gametes and embryos from Carnivora

In addition to companion animals and laboratory species, about 270 carnivore species play fundamental ecological roles in different ecosystems. However, almost 40% of carnivore species are now threatened or endangered in the wild because of human activities. While protection of natural habitats is critical, it is equally important to better understand carnivore reproduction, including a solid knowledge in sperm, oocyte, and embryo biology, to maintain sustainable populations in the wild and in conservation breeding centers. Characterizing gamete and embryo biology is also needed to develop cryopreservation and assisted reproductive technologies to enhance conservation efforts. The objective of this review is to provide the most recent knowledge in the biology of sperm cells, oocytes, and early embryos across all carnivore families. Overall, most data originate from populations maintained in breeding centers or zoos. Characterizations of sperm biology and cryopreservation are far more advanced than for oocytes and embryos. Currently, sperm biology is mainly studied in Canids, Felids, Ursids, and Mustelids, with more emphasis on structural than functional properties. Importantly, fundamental studies of gamete and embryo biology in domestic dogs, cats, and ferrets have paved the way for more precise characterizations in wild counterparts as well as the development of cryopreservation and assisted reproductive technologies. A striking feature of spermatozoa across a wide range of Canids and Felids is the presence of teratospermia (>60% of abnormal sperm cells), which is related to the loss of genetic diversity in some populations. Although sperm structures differ across carnivore families, sperm biology remains difficult to compare because of the small amount of data in many species. Regarding oocyte biology and embryology, data are much scarcer than in sperm cells, with too few studies going beyond structural descriptions. More carnivore species and more individuals (especially from wild populations in addition to captive ones) must be studied to improve our understanding about comparative germplasm biology and develop adequate conservation breeding strategies including the use of cryobanking and assisted reproductive technologies.

Learning strategies and long-term memory in Asian short-clawed otters (Aonyx cinereus)

Social learning, where information is acquired from others, is taxonomically widespread. There is growing evidence that animals selectively employ 'social learning strategies', which determine e.g. when to copy others instead of learning asocially and whom to copy. Furthermore, once animals have acquired new information, e.g. regarding profitable resources, it is beneficial for them to commit it to long-term memory (LTM), especially if it allows access to profitable resources in the future. Research into social learning strategies and LTM has covered a wide range of taxa. However, otters (subfamily Lutrinae), popular in zoos due to their social nature and playfulness, remained neglected until a recent study provided evidence of social learning in captive smooth-coated otters (Lutrogale perspicillata), but not in Asian short-clawed otters (Aonyx cinereus). We investigated Asian short-clawed otters' learning strategies and LTM performance in a foraging context. We presented novel extractive foraging tasks twice to captive family groups and used network-based diffusion analysis to provide evidence of a capacity for social learning and LTM in this species. A major cause of wild Asian short-clawed otter declines is prey scarcity. Furthering our understanding of how they learn about and remember novel food sources could inform key conservation strategies.

Quantification of immunoreactive testosterone and estradiol-17ß metabolites to identify the sex of Neotropical otters (Lontra longicaudis annectens) in the field

Before there was use of ultrasonographic imaging, determination of the ratio of estrogens to androgens in the same individual was a technique used for differentiating the sex of monomorphic animals in captivity, with larger estrogen concentrations in the females. Due to species-specific differences in both concentration and changes throughout the year of these hormones, corroboration of the method is needed in each case. In this study, there was use of a chemo-immuno assay to quantify sex steroids in fecal samples collected from seven (five females and two males) Neotropical otters, Lontra longicaudis. The reproductive season for this species was determined to be between October and March, with increased estradiol in the females and relatively greater concentrations of testosterone in the males as compared with other seasons of the year. Results from utilization of a k-means analysis procedure indicated that the use of steroid ratios in fecal samples to differentiate otter sex is an effective technique when there are evaluations during the breeding season. The estrogen to androgen ratios during this period, however, are the inverse of what was expected, with there being larger testosterone concentrations in the female otters. The ratio of estrogens to androgens in feces of captive otters can be effectively used to determine the sex of otters in the field. We propose this method is reliable for sex determination in wild otter populations during the reproductive season.

River otters (Lontra canadensis) "trapped" in a coastal environment contaminated with persistent organic pollutants: Demographic and physiological consequences

Productive coastal and estuarine habitats can be degraded by contaminants including persistent organic pollutants (POPs) such as PCBs, dioxins, and organochlorine insecticides to the extent of official designation as contaminated sites. Top-predatory wildlife may continue to use such sites as the habitat often appears suitable, and thus bioaccumulate POPs and other contaminants with potential consequences on their health and fitness. Victoria and Esquimalt harbours are located on southern Vancouver Island, British Columbia (BC) and are federally designated contaminated sites due mainly to past heavy industrial activities, such as from shipyards and sawmills. We collected scat samples from river otters (Lontra canadensis) throughout an annual cycle, and combined chemical analysis with DNA genotyping to examine whether the harbour areas constituted a contaminant-induced ecological trap for otters. We confirmed spatial habitat use by radio telemetry of a subsample of otters. Fifteen percent of otter scat contained PCB concentrations exceeding levels considered to have adverse effects on the reproduction of mink (Neovison vison), and there were significant positive correlations between concentrations of PCBs and of thyroid (T3) and sex (progesterone) hormones in fecal samples. Radio telemetry data revealed that otters did not show directional movement away from the harbours, indicating their inability to recognize the contaminated site as a degraded habitat. However, analysis and modeling of the DNA genotyping data provided no evidence that the harbour otters formed a sink population and therefore were in an ecological trap. Despite the highly POP-contaminated habitat, river otters did not appear to be adversely impacted at the population level. Our study demonstrates the value of combining chemical and biological technologies with ecological theory to investigate practical conservation problems.

Noninvasive monitoring of female reproductive hormone metabolites in the endangered European mink (Mustela lutreola)

This study examined the reproductive physiology of female European mink (Mustela lutreola) to augment the available information on estrus, ovulation, and pregnancy with the long-term goal of supporting ex situ breeding management of this highly endangered species. Fecal reproductive hormone metabolites were measured using EIAs for estrogen and 20-oxo-pregnane metabolites. Seasonal hormone profiles were established. A comparison of hormone fluctuations in pregnant and nonpregnant females showed that both estrogen and 20-oxo-pregnane metabolites were significantly elevated during gestation, which is 42 days in length. Delayed implantation or embryonic diapause does not occur in this species. Litter size was correlated with 20-oxo-pregnane levels but not with estrogen concentrations. During lactation, 20-oxo-pregnane metabolite levels remained higher than in nonpregnant females. The breeding season was characterized by peaks in vaginal cornified cells and fecal estrogen metabolite levels. Up to four peaks in estrogen levels were identified and confirmed that European mink are seasonally polyestrous. The results of 20-oxo-pregnane measurements indicated that hCG can be applied to induce ovulation. With the establishment of this noninvasive method, we present a new tool to support population management of this species.

Reversible meiotic arrest in feline oocytes

Increasing intracellular concentrations of cyclic adenosine monophosphate (cAMP) within the cumulus-oocyte complex (COC) inhibits or delays spontaneous oocyte maturation and improves the developmental competence of the oocyte in many species, but information for carnivores is limited. The objectives of the present study were to describe the effects of isobutyl methylxanthine (IBMX), which decreases cAMP degradation, and forskolin, which increases cAMP production, on spontaneous and induced maturation (by equine chorionic gonadotrophin (eCG) and epidermal growth factor (EGF)) of feline oocytes and to evaluate the reversibility of IBMX-induced arrest by measuring the resumption of meiosis and embryonic development following IVF. IBMX decreased (P<0.05) the incidence of spontaneous (6.7% vs 42.0%, metaphase II (MII)) and induced (5.6% vs 66.1% MII) maturation after 24 h of culture. In contrast, forskolin stimulated meiosis (81.7% MII; P<0.05). Following 12 h of culture with IBMX and an additional 24h with eCG and EGF in the absence of IBMX, the proportions of oocytes reaching MII (66.1%), cleaving (79.9%) and developing to the blastocyst stage (15.3%) were similar (P>0.05) to oocytes cultured continuously with eCG and EGF (70.2%, 83.0% and 18.1%, respectively). These results demonstrate that IBMX reversibly inhibits both spontaneous and eCG+EGF-induced meiosis in feline oocytes without compromising the oocyte's developmental competence.

Long-term trends in reproductive and demographic parameters of female Northwest Atlantic hooded seals (Cystophora cristata): population responses to ecosystem change?

More than 2500 ovaries were collected from Northwest Atlantic hooded seals ( Cystophora cristata (Erxleben, 1777)) in the period 1956–2006 during moulting (data blocks: 1956–1960, 1970–1972, 1978), postmoulting (data blocks: 1990–1994, 1996–2006), and whelping (data blocks: 1967–1972, 1973–1976, 1979, 1983–1987, 1989–1995). Mean age at primiparity (MAP) was estimated as the mean age of females with a single corpus albicans or a corpus luteum from a postimplantation pregnancy. MAP was stable at 4.2–4.5 years during 1956–1978, increasing to 4.9–5.2 years in 1979 and to 6.1 years in 1989–1995 (later data insufficient). Patterns of corpus accumulation indicated occasional skipped pregnancies. This may have affected the accuracy of MAP estimates but not the main trends. Declining proportions of parae younger than 10 years after 1979 are consistent with effects of delayed maturation, reduced adult hunting mortality, and (or) increased juvenile mortality. From the 1990s, declining adult pregnancy rates are suggested by decreasing trends in proportions of older multiparae (8+) and other ovary-based proxies for pregnancy rates. Hooded seal abundance was largely stable from 1960 to the mid-1990s and changes in population parameters over this period are therefore more likely due to effects of ecosystem change on per-capita resource levels than population-mediated density dependence.

Characterizing gonadal and adrenal activity by fecal steroid analyses in pygmy rabbits (Brachylagus idahoensis)

In 2001, the sudden collapse of the Columbia Basin population of pygmy rabbits prompted the initiation of a captive breeding program to facilitate reintroduction, but reproductive success in captivity has not met expectations. Therefore, the objective of this study was to characterize the reproductive and adrenal endocrinology of this endangered rabbit species so that appropriate management strategies could be developed to monitor animal welfare and increase reproduction. Fecal samples were collected from 27 female pygmy rabbits over three breeding and non-breeding seasons. HPLC analyses verified the presence of progesterone in the excreta of pygmy rabbits, but the majority of progestagen metabolites were unidentified polar compounds. By contrast, >70% of glucocorticoid immunoactivity was associated with cortisol. Longitudinal fecal hormone profiles during pregnancy were characterized by a large spike in progestagens shortly after mating, a gradual increase in progestagen and glucocorticoid concentrations throughout gestation and a return of hormones to baseline soon after birth (Day 24). The spike in progestagens 1 day after mating was a significant discovery for this species and appears to provide a reliable means of determining if a successful mating has occurred. Seasonal analyses of hormone excretion found that progestagen baselines did not vary between the breeding and non-breeding seasons, but, as expected, were highest during the breeding season in association with pregnancy. Across seasons, the lowest concentrations of glucocorticoids were associated with the highest rates of offspring production and survival, suggesting a possible link between heightened adrenal activity and lowered reproductive fitness in pygmy rabbits.

Sex differences in spatial ability: a test of the range size hypothesis in the order Carnivora

Sex differences in spatial cognition have been reported for many species ranging from voles to humans. The range size hypothesis predicts that sex differences in spatial ability will only occur in species in which the mating system selects for differential range size. Consistent with this prediction, we observed sex differences in spatial ability in giant pandas, a promiscuous species in which males inhabit larger ranges than females, but did not observe sex differences in Asian small-clawed otters, a related monogamous species in which males and females share home ranges. These results provide the first evidence of sex differences in spatial ability in the order Carnivora, and are consistent with the range size hypothesis.

Reproductive features and faecal progesterone metabolite profile in female ferrets

Elevated post-partum progesterone metabolite (P(4) -met) levels have been recently postulated to occur in lactating lynxes. The aims of this study were to monitor reproductive features in female ferrets, changes in the faecal P(4) -met concentrations throughout the breeding season and ovarian activity in post-partum lactating and non-lactating (NL) female ferrets. Our results indicate that coinciding with the results described in the lynx, elevated faecal P4-met concentrations occur in lactating ferrets, furthermore, that the duration of elevated secretion of P(4) seems to be dependent on the duration of lactation (P4-met at delivery, n=47: <500 ng/g; 5-7 days after delivery, during lactation, n=47: ≥ 500-800 ng/g; in females weaned at delivery, n=4: baseline levels). Three days after ovariohysterectomy of lactating females, P(4) -met concentrations decreased to baseline levels. In lactating females, the ovarian stroma is more active than that in NL ones implicating that the ovary is at least in part responsible for the elevated P4-met concentrations. Ovaries of lactating females contained many luteinized cells either as luteinized granulose cells in the wall of late pre-antral/early antral follicles or as corpus luteum (CL)-like structures. Early resumption of the entire ovarian activity (developed follicles and oestrus) occurs in NL post-partum females, while final follicular development is blocked (follicles stalls at antral stage) in the lactating ones (however, occasionally lactational oestrus may occur). We suppose that the elevated faecal P4-met during lactation together with suckling and other hormonal effects may contribute to prevention of early returning to oestrus in nursing female ferrets.

Fecal endocrine profiles and ejaculate traits in black-footed cats (Felis nigripes) and sand cats (Felis margarita)

Information regarding the reproductive biology of black-footed cats (BFC) and sand cats (SC) is extremely limited. Our objectives were to: (1) validate fecal hormone analysis (estrogens, E; progestagens, P; androgens, T) for noninvasive monitoring of gonadal activity; (2) characterize estrous cyclicity, ovulatory mechanisms, gestation, and seasonality; and (3) evaluate male reproductive activity via fecal androgen metabolites and ejaculate traits. In both species, the estrous cycle averaged 11-12 days. In BFC (n=8), estrus lasted 2.2+/-0.2 days with peak concentrations of E (2962.8+/-166.3 ng/g feces) increasing 2.7-fold above basal concentrations. In SC (n=6), peak concentrations of E (1669.9+/-83.5 ng/g feces) during estrus (2.9+/-0.2 days) were 4.0-fold higher than basal concentrations. Nonpregnant luteal phases occurred in 26.5% (26 of 98) of BFC estrous cycles, but were not observed in SC (0 of 109 cycles). In both species, P concentrations during pregnancy were elevated (32.3+/-3.0 microg/g feces BFC; 8.5+/-0.7 microg/g feces SC) approximately 10-fold above basal concentrations. Fecal T concentrations in males averaged 3.1+/-0.1 microg/g feces in BFC and 2.3+/-0.0 microg/g feces in SC. Following electroejaculation, 200 to 250 microl of semen was collected containing 29.9 (BFC) to 36.5 (SC)x10(6) spermatozoa with 40.4 (SC) to 46.8 (BFC)% normal morphology. All females exhibited estrous cycles during the study and spermatozoa were recovered from all males on every collection attempt, suggesting poor reproductive success in these species may not be due to physiological infertility.