Steven L. Monfort

Stress and the suppression of subordinate reproduction in cooperatively breeding meerkats

In many animal societies, dominant individuals monopolize reproduction, but the tactics they employ to achieve this are poorly understood. One possibility is that aggressive dominants render their subordinates infertile by inducing chronic physiological “stress.” However, this hypothesis has been discarded largely for cooperatively breeding species, where reproductive monopolies are often extreme. Here we provide strong support for the stress-related suppression hypothesis in a cooperative mammal, the meerkat (Suricata suricatta). When pregnant, dominant females subject some subordinate females to escalating aggression, culminating in temporary evictions from the group. While evicted, subordinate females suffer chronic elevation of their glucocorticoid adrenal hormone levels, reproductive down-regulation (reduced pituitary sensitivity to gonadotropin-releasing hormone), reduced conception rates, and increased abortion rates. Rather than constantly harassing all subordinate females, dominants only become aggressive when pregnant themselves (when subordinate reproduction would otherwise conflict with their own) and target those females with whom reproductive conflict is most likely (older, pregnant, and more distantly related females). Our findings suggest that dominant female meerkats employ stressful evictions to suppress reproduction among their probable competitors, when attempting to breed themselves. Given the lack of evidence for stress-related suppression in other cooperative breeders to date, it is clear that social stress alone cannot account for the reproductive failure of subordinates across such societies. However, our findings raise the possibility that, in some cooperative breeders at least, dominants may employ stress-related suppression as a backup mechanism to guard against lapses in reproductive restraint by their subordinates.

Genome Resource Banks

B iological diversity is the key to maintaining life as we know it (Wilson 1992). However, rapidly growing human populations place extraordinary pressures on ecosystems, such as large-scale environmental destruction, habitat conversion, habitat fragmentation, and pollution. One reaction to these problems has been the emergence of conservation biology, an assemblage of scientific disciplines that are focused on sustaining biodiversity through a cooperative synthesis of ideas, information, and approaches. Virtually all conservation biologists agree that habitat preservation is the best way to conserve biodiversity. Setting aside large tracts of land so that they are free from human interference can protect many species, but this approach has also been charac-

Behavioural and endocrine mechanisms of reproductive suppression in Serenge dwarf mongooses

Behavioural, demographic and endocrine data were collected from a wild population of dwarf mongooses, Helogale parvula, in Serengeti National Park, Tanzania. The data show that subordinate females are reproductively suppressed by a complex of endocrine and behavioural mechanisms, while subordinate males are reproductively suppressed primarily by behavioural mechanisms. Subordinate females have (1) low baseline oestrogen levels, (2) low mating rates, and (3) low peak oestrogen levels during mating periods. Subordinate males (1) have low mating rates, and (2) are the recipients of increased aggression during mating periods, but (3) have androgen levels indistinguishable from those of dominants, both during and away from mating periods. Mechanistic differences between the sexes suggest that the selection pressures favouring reproductive suppression may also differ between the sexes.

Embryogenesis in conservation biology — Or, how to make an endangered species embryo

Abstract Embryo technologies have not as yet contributed to practical conservation of rare wildlife species. Production of young following artificial insemination (AI), embryo transfer (ET) or in vitro fertilization (IVF) has been sporadic, and it is now clear that biological differences among species limit our abilities to adapt these techniques easily to rare species. Nonetheless, there is encouraging progress at two levels. First, there is more acceptance that rare wildlife species safely tolerate the manipulations necessary to collect basic reproductive information or to test artificial breeding. This has increased access to rare animal populations and helped develop organized captive breeding programs, many of which emphasize the need for more research. Secondly, a gradually developing database about how these species reproduce is driving more systematic experimentation and artificial breeding attempts. Studies in our laboratory focus on producing embryos in vivo or in vitro. When essential information is available on fundamental reproductive processes, and, especially when comparative data are available from a domesticated animal model, then AI techniques are adapted to the endangered species. When few data are available, then studies emphasize using IVF (often in combination with in vitro oocyte maturation) to examine the factors regulating embryo formation and viability. These strategies are illustrated by recent progress involving (i) AI of select species of cervids, felids and mustelids, (ii) oocyte maturation in felids and (iii) IVF and ET in felids. Offspring have been produced, but perhaps more important are the answers to fundamental and mechanistic questions about why some wildlife species thrive and others do not. If reality-based conservation is defined as a continual data-gathering process that assimilates any and all information ultimately useful for preserving species, then embryo technologies are making considerable contributions to conservation biology.

The effect of immunocontraception on the behavior and reproduction of white-tailed deer

Behavioral and reproductive consequences of porcine zona pellucida (PZP) immunocontraception were examined in a herd of white-tailed deer (Odocoileus virginianus; n = 30) from September 1992 to September 1994. Does were captured from a wild population and placed within either of 2 large (32-ha total) wooded enclosures. Does were administered either: (1) a single injection containing PZP-emulsified in Freunds complete adjuvent (FCA) and microsphere-encapsulated PZP; (2) 2 injections of PZP-emulsified in FCA and Freunds incomplete adjuvant (FIA), 4 weeks apart; or (3) no treatment. Mature, spermic bucks (n = 5) were added to each pasture 4 weeks after the final PZP treatment, and reproductive behaviors and fawn production were observed for 2 years. Immunocontracepted females exhibited increased activity compared to non-treated females, presumably reflecting an increased number of estrus intervals. Similarly, enclosure bucks exhibited an extended breeding season compared to males in the surrounding wild population. The 2-injection PZP regimen provided effective contraception during both years of the study. The 1-injection PZP regime provided effective contraception only during the second year, following administration of a PZP booster. Histological evaluations of ovaries failed to reveal among-group differences in ovarian architecture. Contracepted-nonpregnant does gained significantly more weight than control females during the study.

Steroid metabolism and validation of noninvasive endocrine monitoring in the African wild dog (Lycaon pictus)

The purpose of this study was to validate noninvasive endocrine monitoring techniques for African wild dogs (Lycaon pictus) and to establish physiological validity of these methods by evaluating longitudinal reproductive-endocrine profiles in captive individuals. To determine the primary excretory by-products of ovarian steroid metabolism, [14C]-progesterone and [3H]-estradiol were co-administered to a female and all excreta were collected for 80 hr postinjection. Radiolabel excretion peaked ≤ 18 hr postinfusion, and progesterone and estradiol metabolites were excreted in almost equivalent proportions in urine (39.7 and 41.1%, respectively) and feces (60.3 and 58.9%, respectively). Most of the urinary metabolites were conjugated (estradiol, 94.3 ± 0.3%; progesterone, 90.4 ± 0.5%), so that immunoassays for pregnanediol-3α-glucuronide (PdG) and estrogen conjugates (EC) were effective for assessing steroid metabolites. Two immunoreactive estrogens (estradiol and estrone) and at least one immunoreactive progesterone metabolite (3α-hydroxy-5α, pregnan-20-one) were detected in feces. Urine and fecal samples were collected (1–3 times per week) for 1.5 yr from one adult female and two adult males to assess longitudinal steroid metabolite excretion. Overall correlation of urinary PdG to matched, same-day fecal progesterone metabolites immunoreactivity was 0.38 (n = 71, P < 0.05). Similarly, urinary EC was correlated (P < 0.05) with same-day fecal estrogen immunoreactivity (r = 0.49, n = 71). During pregnancy and nonpregnant cycles, copulation occurred at the time of peak (or declining) estrogen metabolites and increasing progesterone metabolites concentrations. Estrus duration was 6–9 days and gestation lasted 69 days with parturition occurring coincident with a drop in progesterone metabolites. Males exhibited seasonal trends in fecal testosterone excretion with maximal concentrations from July to September coincident with peak mating activity. Although these limited longitudinal hormone profiles should be interpreted cautiously, noninvasive gonadal steroid monitoring suggests that: (1) both female and male wild dogs may exhibit reproductive seasonality in North America, (2) females are monoestrous, and (3) peak testicular activity occurs between August and October coincident with mating behavior. From a conservation perspective, noninvasive endocrine monitoring techniques should be useful for augmenting captive breeding programs, as well as for developing an improved understanding of the physiological mechanisms underlying reproductive suppression in response to social and ecological pressures. Zoo Biol 16:533–548, 1997.

Reproductive Physiology and Development of Artificial Insemination Technology in Killer Whales (Orcinus orca)

Abstract Research was conducted to define the basic reproductive physiology of killer whales (Orcinus orca) and to use this knowledge to facilitate the development of artificial insemination procedures. The specific objectives were 1) to determine the excretory dynamics of urinary LH and ovarian steroid metabolites during the estrous cycle; 2) to evaluate the effect of an exogenously administered, synthetic progesterone analog on reproductive hormone excretion; 3) to validate the use of transabdominal ultrasound for ovarian evaluation and timing of ovulation; 4) to examine the quality of semen after liquid storage and cryopreservation; and 5) to develop an intrauterine insemination technique. Based on urinary endocrine monitoring of 41 follicular phases and 26 complete cycles from five females, estrous cycles were 41 days long and comprised a 17-day follicular phase and a 21-day luteal phase. A consistent temporal relationship was observed between peak estrogen conjugates and the LH surge, the latter of which occurred approximately 0.5 days later. Two animals placed on oral altrenogest (three separate occasions for 30, 17, and 31 days, respectively) excreted peak urinary estrogen concentrations 25 days after withdrawal that were followed by sustained elevations in urinary pregnanediol-3α-glucuronide excretion. Mean preovulatory follicle diameter was 3.9 cm (n = 6), and ovulation occurred 38 h (n = 5) after the peak of the LH surge. Based on visual estimates of motility, liquid-stored semen maintained 92% of its raw ejaculate sperm motility index (total progressive motility × kinetic rating [0–5 scale, where 0 = no movement and 5 = rapid progressive movement]) when held at 4°C for 3 days postcollection. Semen cryopreserved using a medium freezing rate demonstrated good postthaw total motility (50%), progressive motility (94%), and kinetic rating (3.5). Insemination during eight estrous cycles resulted in three pregnancies (38%), two from liquid-stored and one from cryopreserved semen. Two calves were delivered after gestation lengths of 552 and 554 days, respectively. These data demonstrate the potential of noninvasive endocrine monitoring combined with serial ultrasonography to improve our understanding of the reproductive biology of cetaceans. This fundamental knowledge was essential for ensuring the first successful conceptions, resulting in live offspring, using artificial insemination in any cetacean species.

Phylogeography and conservation genetics of Eld's deer (Cervus eldi)

Elds deer (Cervus eldi) is a highly endangered cervid, distributed historically throughout much of South Asia and Indochina. We analysed variation in the mitochondrial DNA (mtDNA) control region for representatives of all three Elds deer subspecies to gain a better understanding of the genetic population structure and evolutionary history of this species. A phylogeny of mtDNA haplotypes indicates that the critically endangered and ecologically divergent C. eldi eldi is related more closely to C. e. thamin than to C. e. siamensis, a result that is consistent with biogeographic considerations. The results also suggest a strong degree of phylogeographic structure both between subspecies and among populations within subspecies, suggesting that dispersal of individuals between populations has been very limited historically. Haplotype diversity was relatively high for two of the three subspecies (thamin and siamensis), indicating that recent population declines have not yet substantially eroded genetic diversity. In contrast, we found no haplotype variation within C. eldi eldi or the Hainan Island population of C. eldi siamensis, two populations which are known to have suffered severe population bottlenecks. We also compared levels of haplotype and nucleotide diversity in an unmanaged captive population, a managed captive population and a relatively healthy wild population. Diversity indices were higher in the latter two, suggesting the efficacy of well‐designed breeding programmes for maintaining genetic diversity in captivity. Based on significant genetic differentiation among Elds deer subspecies, we recommend the continued management of this species in three distinct evolutionarily significant units (ESUs). Where possible, it may be advisable to translocate individuals between isolated populations within a subspecies to maintain levels of genetic variation in remaining Elds deer populations.

Monitoring reproduction in captive moose using urinary and fecal steroid metabolites

Because repeated capture, restraint, and blood sampling generally are impractical strategies for monitoring reproductive status in wildlife species, noninvasive methods for tracking reproductive activity have become increasingly important. Thus, we used radioimmunoassay (RIA) of urinary pregnanediol-3α-glucuronide (PdG), estrogen conjugates, and fecal progesterone and estradiol to assess estrous cycles and pregnancy in captive moose (Alces alces). Using urinary PdG, we identified distinct reproductive cycles that began during October, and estrus behavior that coincided with nadirs in PdG excretion. Although PdG increased up to 5-fold over cycling levels during pregnancy, concentrations were variable making pregnancy diagnosis equivocal using this method

Stress and the costs of extra-territorial movement in a social carnivore

Costs associated with extra-territorial movement are believed to have favoured the evolution of delayed dispersal and sociality across a range of social vertebrates, but remain surprisingly poorly understood. Here we reveal a novel mechanism that may contribute substantially to the costs of extra-territorial movement: physiological stress. We show that subordinate male meerkats, Suricata suricatta, exhibit markedly elevated faecal glucocorticoid metabolite levels (a non-invasive measure of hypothalamic–pituitary–adrenal axis activity) while conducting extra-territorial prospecting forays. While brief increases in glucocorticoid levels are unlikely to be costly, chronic elevations, arising from prolonged and/or frequent forays, are expected to compromise fitness through their diverse negative effects on health. Our findings strongly suggest that prolonged extra-territorial movements do result in chronic stress, as the high glucocorticoid levels of prospectors do not diminish on longer forays and are no lower among males with greater prospecting experience. A generalized ‘stress’ of extra-territorial movement may therefore have strengthened selection for delayed dispersal and sociality in this and other species, and favoured the conduct of brief forays over extended periods of floating. Our findings have implications too for understanding the rank-related distribution of physiological stress in animal societies, as extra-territorial movements are often conducted solely by subordinates.