Use of behavioral measures to assess reproductive status in maned wolves (Chrysocyon brachyurus)

Captive breeding efforts of the threatened maned wolf (Chrysocyon brachyurus) have been plagued by a lack of reliable reproduction and a high rate of neonatal mortality. A particular problem for animal managers has been the ability to detect pregnancy in a noninvasive manner. Pseudopregnancies are common, and many staff hours are expended preparing for a birth that may not occur. The objectives of our study were to document changes in behavior during the breeding season in captive maned wolves in order to determine if behaviors other than sexual (i.e., copulation) could be used to distinguish nonbreeding from breeding pairs and, further, whether successful breeding pairs (young born) could be distinguished behaviorally from breeding pairs that did not produce young (pseudopregnant). Between 1988 and 1994, behavioral data were collected during the annual reproductive season from 52 maned wolf pairings (27 males, 26 females) housed at 17 North American institutions. Breeding animals showed significant increases in rates of affiliative behaviors (approach, friendly) and the amount of time spent in close association (social) during the estrous period, compared to pre- and post-estrous periods. In contrast, the behavior of nonbreeding pairs varied little throughout the breeding season. Discriminant function analysis (DFA) showed that several behavioral measurements during certain reproductive periods were useful in discriminating between nonbreeding and breeding animals (rates of friendly and social behavior for males, marking and social behavior for females). Unsuccessful (pseudopregnant) and successful breeding pairs could be further distinguished on the basis of agonistic and approach behavior frequencies (successful females showed higher rates of agonistic and lower rates of approach behavior during certain periods; successful males had higher rates of both behaviors). Discriminant equations for key behavioral measurements and examples of their practical application are presented. DFA provides animal managers with an effective, noninvasive technique for assessing the reproductive status of maned wolf pairs. © 1996 Wiley-Liss, Inc.     

Physiological pineal effects on female reproductive function of laboratory rats: prenatal development of pups, litter size and estrous cycle in middle age

The present study investigates whether and how the pineal or its hormone melatonin influences female reproductive functions, namely the litter size, prenatal development of offsprings, and estrous cyclicity, especially its age-related cessation in a non-seasonal breeder, the laboratory rat. Wistar rats were maintained under a 24 h light-dark (12Lratio12D) cycle. Female rats were divided into 3 groups: non-operated (NO), sham-operated (SX), and pinealectomized (PX). Surgeries were performed in 35-40 day-old females. Starting at an age between 70 days and 7 months, female rats of all 3 groups were repeatedly mated with intact males. PX mothers more frequently delivered pups with malformations (e.g., taillessness, hydronephrosis, 7 out of 1263 pups) than control rats (0/1323; p<0.007). In the first delivery at 3 months of age, but not at later ages, PX mothers delivered more pups of lower body weight than control animals (p<0.001). Examination of vaginal smears showed that almost all female rats of the NO, SX, and PX groups had 4-day estrous cyclicity when they were young-between 60 days and 5 months of age. At an age of 17 to 18 months, most female rats of the NO and SX groups showed irregular, continuously diestrous or pseudopregnancy-like patterns, and 4-day estrous cyclicity was found in only 10% of the NO or SX animals. In contrast, about 50% of the PX rats showed 4-day estrous cyclicity at this older age (p< 0.001). Melatonin, when added to drinking water (0.4 mg/L) for 16 days during the dark phase increased the frequency of diestrous phase, except in continuously diestrous rats and very few others. This melatonin effect was strong in PX rats but relatively weak in SX rats. In conclusion, the pineal hormone appears to influence various reproductive functions and developmental processes, especially pregnancy and the timing of reproductive aging in rats. The effects of pinealectomy are more prominent at an age of 60 to 80 days (i.e., shortly after puberty) and at the beginning of the cessation of cycles in middle-aged females.     

Observations on reproduction,hormones, copulatory behavior,and neonatal mortality in captive Lemur mongoz (Mongoose lemur)

This study examines correlates of reproduction in Lemur mongoz, an endangered prosimian primate with a history of poor captive reproduction. Male testicular growth and regression were quantified via testicular indices (TI). Although TIs could be used to predict male breeding condition, they were not indicators of ability to sire offspring. Serum estradiol (E₂) and progesterone (P) concentrations, along with vaginal cytology, were used to monitor female reproductive cyclicity. E₂ and P profiles showed no abnormalities. An elevation of E₂ with low P, approximately one estrous cycle length (31.4 days) prior to the onset of fertile cycles, was consistent with the phenomenon of ‘pseudoestrus’ observed in other lemur species. The copulatory pattern, consisting of thrusting, multiple intromissions, single or multiple ejaculations, and no copulatory lock, was more complex than expected for an animal with a supposedly monogamous mating system. The preference for natural arboreal substrata during copulation suggests that enclosure furnishings may influence copulatory behavior. A 30% neonatal mortality rate tempered recent success in breeding L. mongoz at the Duke University Primate Center (DUPC). Although infant sex and parity of the mother were not predictive of neonatal mortality, mother's natal status was, with captive-born females having a 67% infant mortality rate, compared with 15% in wild-caught females. Based on these observations, a number of factors, including housing, behavior, and photoperiod, may be relevant to successful captive propagation of L. mongoz. © 1992 Wiley-Liss, Inc.     

Factors influencing reproductive success and litter size in captive island foxes

A severe decline of island foxes (Urocyon littoralis) on the northern Channel Islands in the 1990s prompted the National Park Service to begin a captive breeding program to increase their numbers. Using detailed records of all the fox pairs (N = 267) that were part of the program on San Miguel, Santa Rosa, and Santa Cruz Islands from its inception in 2000 through 2007, we identified factors influencing the breeding success of pairs in captivity in the interest of formulating strategies that could increase captive productivity. We compiled a database of variables including litter size, reproductive success, distance to nearest occupied pen during the breeding season, subspecies, exposure, female age, male age, age difference, female and male origin (wild vs. captive born), same versus different origin, years paired, previous reproductive success by the pair, previous reproductive success by the female, mate aggression-related injuries, male previous involvement in a pair with mate aggression, and female previous involvement in a pair with mate aggression. We used multiple linear regression to identify factors predictive of litter size, and logistic regression to predict the probability of reproductive success. A larger inter-pen distance, older male age, less exposure, and a smaller intra-pair age difference positively affected litter size. The probabilities of reproductive success increased with fewer years paired and less exposure. Comparatively, pairs with wild born females (vs. captive born females), and previously successful pairs (vs. previously unsuccessful and new pairs) were most likely to be successful. These results indicate that the optimal situation was to pair wild-caught females with older males in sheltered pens that were as far from other pens as possible, to maintain successful pairs and repair unsuccessful ones. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

The relation of ovarian steroid levels in young female rats to subsequent estrous cyclicity and reproductive function during aging

In multiparous rats, the incidence of regular estrous cyclicity and fertility decreases markedly at middle age. However, recent studies have shown that repeated pregnancies or progesterone (P) implants can subsequently cause retired breeder females to maintain regular cyclicity for an extended period of time; these results suggest a P-mediated deceleration of reproductive aging. In the present study, we examined the relation of ovarian steroid levels in young virgin females to their subsequent estrous cyclicity and reproductive function during aging as compared to multiparous females. Beginning at 4 mo of age and continuing to 6 mo of age, regularly cyclic virgin rats received either consecutive P implants (n = 41) or no implants (controls, n = 45) for 3 wk, followed by implant removal for 1 wk. Additional females (n = 72) were mated and allowed to undergo repeated pregnancies at 4, 6 1/2, and 8 mo of age. Blood samples were obtained throughout the estrous cycle (virgin females), during pregnancy (multiparous rats), and on Day 11 of successive treatments with P implants (virgins with P implants) for P, estradiol (E2), and testosterone (T) measurements. Subsequently, regularly cyclic females from all three groups were mated with fertile males to undergo term pregnancies at 10 and 12 mo of age. While the virgin controls showed cyclic increases in P, T, and E2 secretion during their estrous cycles, the P-implanted females had persistently low E2 and high P and T levels during treatment, which indicates an inhibition of ovarian E2 synthesis by P.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aspects of reproduction in the eastern rufous mouse lemur (Microcebus rufus) and their implications for captive management

The eastern rufous mouse lemur is one of the smallest primate species. It inhabits the eastern rain forest of Madagascar. Its reproductive biology has not been examined because of its rarity in laboratories. We present the first data on reproduction and variation in reproductive success from a breeding colony of wild‐caught Microcebus rufus. The eastern rufous mouse lemur shows a seasonal change in testicular size and in the occurrence of estrus. Females had 2.5 cycles (range, one to four) per season. The estrous cycle length was 59 days (range, 51–66), the duration of vaginal opening during estrus was 7.5 days (range, 5–8), receptivity occurred on the third day of estrus, gestation length was 56.5 days (range, 56–57), litter size was two neonates (range, one to three). The frequency and duration of mating behavior varied widely among the pairs. Copulation seemed to occur on a single day per estrus within the first to fourth hour after light change to red light. In four cases (three pairs), copulation lasted between 15 and 240 seconds. Breeding success can be increased by choosing mates carefully. Microcebus rufus seems to be a seasonal breeder like its sibling species Microcebus murinus. In wild‐caught animals, males seemed to adapt quickly (first season) to the conditions of captivity, whereas in the females, individual variation (first to third season) in reproductive activity was observed. Air humidity of >60% seems to facilitate the breeding success in wild‐caught pairs. First pregnancy and successful rearing of offspring occurred in the second and fourth year of captivity in two of three females. Wild‐caught eastern rufous mouse lemurs seemed to demonstrate variation in adapting to the conditions of captivity with regard to sex and individuality. Zoo Biol 20:157–167, 2001. © 2001 Wiley‐Liss, Inc.     

Effects of reproductive state on vocalizations in squirrel monkeys (Saimiri sciureus)

Vocalizations and behavior of a group of 6 squirrel monkeys, 2 males and 4 females, were recorded during the nonbreeding and breeding seasons. Behavioral and physical criteria were used to determine the presence of estrus. During the breeding season the types of vocalizations uttered by estrous females changed, and the adult male increased his rate of vocalizing. Err vocalizations by estrous females were associated with increased following and initiation of affiliative behavior with the adult male, and may have functioned to facilitate these interactions. Errs appeared to be related to changes in female reproductive state rather than to the behavior of others. The adult male increased vocalizations associated with sexual and aggressive behavior (squeals and cackles), primarily in response to the estrous females' persistent initiation of interactions with him. We concluded that certain vocalizations in Saimiri reflected changes in the reproductive state of males and females, and functioned to mediate changes in social bonding during the breeding season.     

Characterization of the estrous cycle and reproductive traits of the aoudad (Ammotragus lervia) in captivity

In this study the estrous cycle of the aoudad has been analyzed and characterized for the first time, using non-invasive methods for tracking reproductive cyclicity. The duration of the estrous cycle is 23 days (range 16-32 days), with a luteal phase of 17 days (range 12-27 days) and an interluteal phase of 6 days (range 3-14 days). The estrous cycle did not differ between females, but it was affected by the time of the year. Intraindividual variation of the cycle was observed in one out of the nine individuals. The average hormone concentration values, the estrogen:progestogen ratio, as well as their minimum and maximum values for each interluteal and luteal phases of the estrous cycle, are shown. Interindividual differences found in these values were basically associated with age. Females tended to start their cycle when in the presence of an adult male. Anestrus was observed in study females except for the oldest (14 years old). Age and anestrus onset were correlated, with younger females starting earlier than the older ones. This study reveals that Ammotragus reproductive biology is more similar to that of Capra than Ovis, except for some endocrinological features.     

Mobility of moose—comparing the effects of wolf predation risk,reproductive status,and seasonality

In a predator–prey system, prey species may adapt to the presence of predators with behavioral changes such as increased vigilance, shifting habitats, or changes in their mobility. In North America, moose (Alces alces) have shown behavioral adaptations to presence of predators, but such antipredator behavioral responses have not yet been found in Scandinavian moose in response to the recolonization of wolves (Canis lupus). We studied travel speed and direction of movement of GPS‐collared female moose (n = 26) in relation to spatiotemporal differences in wolf predation risk, reproductive status, and time of year. Travel speed was highest during the calving (May–July) and postcalving (August–October) seasons and was lower for females with calves than females without calves. Similarly, time of year and reproductive status affected the direction of movement, as more concentrated movement was observed for females with calves at heel, during the calving season. We did not find support for that wolf predation risk was an important factor affecting moose travel speed or direction of movement. Likely causal factors for the weak effect of wolf predation risk on mobility of moose include high moose‐to‐wolf ratio and intensive hunter harvest of the moose population during the past century.     

The reproductive biology of a free-ranging troop of Japanese monkeys

Quantitative data on the reproductive biology of Japanese monkeys (Macaca fuscata), especially of females, are reported here. Arashiyama B troop shows stable annual breeding periodicity, and has mating seasons between October and March. In mating seasons, females show estrus with rather consistent cyclicity, and are in estrus for a total of 35 days on an average. The mean length of estrous cycle is 34 days. Although most females show estrus inter-menstrually, some show peri-menstrually; i.e., estrus does not always synchronize strictly with ovulation. Pubescent females between 3.5 and 6.5 years show estrus, but with low sexual activity. Middle-aged females between 7.5 and 16.5 years show high sexual activity with high conception rate. Old-aged females over 17.5 years show low sexual activity. Females with surviving infants have lower sexual activity than those without infants. There is found no significant correlation between female's ranking and sexual activity. This study was financed partly by the Cooperative Research Fund of the Primate Research Institute, Kyoto University.     

Selected aspects of Lemur variegatus reproductive biology

Results from data collected during the 1978–1979 breeding season on the reproduction of Lemur variegatus at the San Diego Zoo provide information which generally supports previously published reports on this species. Comparison of selected results from these data to a larger data base of which they are a part makes it possible to resolve some of the discrepancies between reports. Certain aspects of the reproductive biology of this species may then be generally characterized with confidence: The onset of seasonal breeding as evidenced by estrous behavior begins as early as mid-December in the northern hemisphere and may continue through March; genital changes associated with estrus in females last 9.85 ± 1.67 days (± SD); female receptivity occurs 7.0 ± 1.53 days after the onset of these genital changes and lasts 12-24 hours, during which breeding occurs; gestation averages 99.47 ± 4.19 days; the peak birth season is April–May; litters normally contain two to three offspring, with full-term neonates weighing an average of 104.63 ± 19.10 grams. In addition, L variegatus appears to be highly resistant to the impact of captivity on both its reproductive physiology and behavior, as indicated by the 100% breeding success of the diversely reared and managed groups of study animals.     

Impacts of the season and reproductive status on fecal reproductive and adrenocortical steroid metabolites in zoo Cuban crocodiles (Crocodylus rhombifer)

Conservation strategies for crocodilians often include captive breeding to create stable assurance populations. Evaluating adrenal and gonadal hormone patterns can provide animal managers with data to more effectively monitor animal welfare and reproductive status. This study evaluated the effects of season (breeding, nesting, or off), sex (male and female), and reproductive status of females (egg-laying/housed with a male or non-laying/housed solo) on concentrations of fecal glucocorticoid metabolite (FGM), fecal androgen metabolite (FAM), and fecal progestogen metabolite (FPM) in seven Cuban crocodiles, Crocodylus rhombifer, at the Smithsonian's National Zoological Park. Overall, seasonal changes in FGM and FPM concentrations were only observed in egg-laying females; FGM and FPM concentrations were both higher during the nesting season compared to the breeding and off seasons. Seasonal changes in FAM concentrations were only observed in males; males had higher FAM concentrations during the breeding and nesting seasons compared to the off season. Future studies investigating the use of fecal hormone metabolites in crocodilians are necessary to understand differences between individuals and species, to further elucidate the interactions between hormones and environmental factors, such as social housing, and to develop long-term datasets for the management of this species.     

The Effects of Breeder Loss on Wolves

Abstract Managers of recovering wolf (Canis lupus) populations require knowledge regarding the potential impacts caused by the loss of territorial, breeding wolves when devising plans that aim to balance population goals with human concerns. Although ecologists have studied wolves extensively, we lack an understanding of this phenomenon as published records are sparse. Therefore, we pooled data (n = 134 cases) on 148 territorial breeding wolves (75 M and 73 F) from our research and published accounts to assess the impacts of breeder loss on wolf pup survival, reproduction, and territorial social groups. In 58 of 71 cases (84%), ≥1 pup survived, and the number or sex of remaining breeders (including multiple breeders) did not influence pup survival. Pups survived more frequently in groups of ≥6 wolves (90%) compared with smaller groups (68%). Auxiliary nonbreeders benefited pup survival, with pups surviving in 92% of cases where auxiliaries were present and 64% where they were absent. Logistic regression analysis indicated that the number of adult-sized wolves remaining after breeder loss, along with pup age, had the greatest influence on pup survival. Territorial wolves reproduced the following season in 47% of cases, and a greater proportion reproduced where one breeder had to be replaced (56%) versus cases where both breeders had to be replaced (9%). Group size was greater for wolves that reproduced the following season compared with those that did not reproduce. Large recolonizing (>75 wolves) and saturated wolf populations had similar times to breeder replacement and next reproduction, which was about half that for small recolonizing (≤75 wolves) populations. We found inverse relationships between recolonizing population size and time to breeder replacement (r= —0.37) and time to next reproduction (r= —0.36). Time to breeder replacement correlated strongly with time to next reproduction (r=0.97). Wolf social groups dissolved and abandoned their territories subsequent to breeder loss in 38% of cases. Where groups dissolved, wolves reestablished territories in 53% of cases, and neighboring wolves usurped territories in an additional 21% of cases. Fewer groups dissolved where breeders remained (26%) versus cases where breeders were absent (85%). Group size after breeder loss was smaller where groups dissolved versus cases where groups did not dissolve. To minimize negative impacts, we recommend that managers of recolonizing wolf populations limit lethal control to solitary individuals or territorial pairs where possible, because selective removal of pack members can be difficult. When reproductive packs are to be managed, we recommend that managers only remove wolves from reproductive packs when pups are ≥6 months old and packs contain ≥6 members (including ≥3 ad-sized wolves). Ideally, such packs should be close to neighboring packs and occur within larger (≥75 wolves) recolonizing populations.     

Annual reproductive activity of Caiman crocodilus fuscus in captivity

We describe the gonadal and abdominal fat storage cycles for a population of Caiman crocodilus fuscus kept in captivity at a breeding farm. The reproductive cycles of males and females are clearly seasonal. Vitellogenic follicles were observed in females year‐round; however, the follicular growth that produces the preovulatory follicles for the breeding season occurs in November–May (most of the dry season to the beginning of the rainy season). These months correspond with the presence of physiologically reproductive males. Oviposition takes place during the wet season (April–August) and the births occur at the end of this season (September–November). Fat storage was not related to reproductive activity, and did not vary by month or between sexes. Although environmental and hormonal conditions have been improved for these captive animals, they maintain a strongly seasonal reproductive cycle, historically fixed to oviposit in the most favorable period for nest construction and hatching during the rainy season. Zoo Biol 22:121–133, 2003. © 2003 Wiley‐Liss, Inc.     

Physiological Pineal Effects on Female Reproductive Function of Laboratory Rats: Prenatal Development of Pups,Litter Size and Estrous Cycle in Middle Age

The present study investigates whether and how the pineal or its hormone melatonin influences female reproductive functions, namely the litter size, prenatal development of offsprings, and estrous cyclicity, especially its age‐related cessation in a non‐seasonal breeder, the laboratory rat. Wistar rats were maintained under a 24 h light‐dark (12L∶12D) cycle. Female rats were divided into 3 groups: non‐operated (NO), sham‐operated (SX), and pinealectomized (PX). Surgeries were performed in 35–40 day‐old females. Starting at an age between 70 days and 7 months, female rats of all 3 groups were repeatedly mated with intact males. PX mothers more frequently delivered pups with malformations (e.g., taillessness, hydronephrosis, 7 out of 1263 pups) than control rats (0/1323; p<0.007). In the first delivery at 3 months of age, but not at later ages, PX mothers delivered more pups of lower body weight than control animals (p<0.001). Examination of vaginal smears showed that almost all female rats of the NO, SX, and PX groups had 4‐day estrous cyclicity when they were young–between 60 days and 5 months of age. At an age of 17 to 18 months, most female rats of the NO and SX groups showed irregular, continuously diestrous or pseudopregnancy‐like patterns, and 4‐day estrous cyclicity was found in only 10% of the NO or SX animals. In contrast, about 50% of the PX rats showed 4‐day estrous cyclicity at this older age (p< 0.001). Melatonin, when added to drinking water (0.4 mg/L) for 16 days during the dark phase increased the frequency of diestrous phase, except in continuously diestrous rats and very few others. This melatonin effect was strong in PX rats but relatively weak in SX rats. In conclusion, the pineal hormone appears to influence various reproductive functions and developmental processes, especially pregnancy and the timing of reproductive aging in rats. The effects of pinealectomy are more prominent at an age of 60 to 80 days (i.e., shortly after puberty) and at the beginning of the cessation of cycles in middle‐aged females.     

Copulatory Plug Displacement Evidences Sperm Competition in Lemur catta

Male displacement of copulatory (sperm) plugs from female vaginas provides further evidence for sperm competition in ring-tailed lemurs (Lemur catta), a gregarious prosimian species with a multimale, multifemale mating system. During two mating seasons, I studied two groups of free-ranging ring-tailed lemurs on St. Catherines Island, GA, USA. I observed 22 mating pairs in which males achieved penile intromission. Copulatory plug displacement by males occurred in 9 cases. Plugs were displaced during copulation by male penes upon withdrawl following deep vaginal thrusting. In every case of copulatory plug displacement, the male displacing a plug mated to ejaculation with the estrous female. In a mating system in which females typically mate with more than one male during estrous, often in succession, copulatory plug displacement may function to disrupt or preclude other males' successful insemination of estrous females. The effects of sperm plug displacement on paternity in Lemur catta are unknown, as no study had heretofore documented copulatory plug displacement in this species. The first-male mating advantage suggested for Lemur catta should be re-evaluated where mating order is known, and copulatory plug displacement during mating, or lack thereof, is identified. Because there is a tendency for first-mating males to mate-guard for longer periods of time in Lemur catta, the latency period between the first mate's ejaculation and that of subsequent mates may be an important determinant of male fertilization success.     

Sexual behaviour and reproductive competition in male wild and domestic Norway rats

The copulatory behaviour of male wild Norway rats (Rattus norvegicus) exposed individually to females in hormone-induced oestrus is characterized by fewer mounts and intromissions per ejaculatory series, shorter ejaculation latencies, and longer ejaculatory clasps than the copulatory behaviour of domestic males. Competition between wild and domestic males tested simultaneously in pairs produced only minor changes in copulatory behaviour. The reproductive success of wild and domestic male pairs simultaneously exposed to naturally cycling females was nearly equal in both the laboratory and an outdoor enclosure. Genotype of the female had little effect on male copulatory behaviour. The copulatory behaviour of sexually naive and experienced domestic rats did not differ. However, most sexually naive wild males failed to exhibit copulatory behaviour under the test conditions employed.     

Abnormal behaviors,with a special focus on rocking,and reproductive competence in a large sample of captive chimpanzees (Pan troglodytes)

Chimpanzees (Pan troglodytes) are endangered in the wild and may no longer be imported into the United States. Of those animals presently in captivity, candidates for breeding programs must be identified to insure a self-sustaining captive population. Some have suggested that poor reproductive performance might be linked to the performance of abnormal behaviors. In Study 1, three institutions housing breeding colonies of chimpanzees (86 males, 103 females) surveyed their animals for abnormal behaviors, copulatory performance, and, for females, maternal competence. In neither sex was there a positive association between absence of copulation and the presence of any of 18 forms of abnormal behavior. No one abnormal behavior was positively associated with inadequate maternal performance. Contrary to expectations, in both sexes (significantly for females), copulators exhibited more forms of abnormal behaviors than did noncopulators. In contrast, good mothers did show slightly fewer different forms of abnormal behaviors than did inadequate mothers. No specific combination of abnormal behaviors was associated with lack of copulatory performance in either sex or with inadequacy of maternal behavior. Significant sex differences occurred only in 2 of the 18 abnormal behaviors (coprophagy and self-clinging), both with females showing the higher prevalence. In Study 2, the rate of rocking in 5 male and 14 female chimpanzees at the Primate Foundation of Arizona was found to be relatively high among some reproductively competent subjects. Some rocking had forms and contexts indicative of aggressive displays. We conclude that chimpanzees should not be disregarded as potential breeders or as candidates for resocialization and breeding programs solely because they exhibit abnormal behaviors. Anyone involved in assessing well-being needs to be aware of individual differences among animals in the stimuli that may elicit rocking behavior. If they are strangers, they may elicit display rocking which does not indicate a lack of well-being. © 1992 Wiley-Liss, Inc.     

Seasonal variation in male alternative reproductive tactics

Genetic parentage analyses reveal considerable diversity in alternative reproductive behaviours (e.g. sneaking) in many taxa. However, little is known about whether these behaviours vary seasonally and between populations. Here, we investigate seasonal variation in male reproductive behaviours in a population of two‐spotted gobies (Gobiusculus flavescens) in Norway. Male two‐spotted gobies guard nests, attract females and care for fertilized eggs. We collected clutches and nest‐guarding males early and late in the breeding season in artificial nests and used microsatellite markers to reconstruct parentage from a subset of offspring from each nest. We hypothesized that mating, reproductive success and sneaking should be more prevalent early in the breeding season when competition for mates among males is predicted to be higher. However, parentage analyses revealed similar values of mating, reproductive success and high frequencies of successful sneaking early (30% of nests) and late (27% of nests) in the season. We also found that multiple females with eggs in the same nest were fertilized by one or more sneaker males, indicating that some males in this population engage in a satellite strategy. We contrast our results to previous work that demonstrates low levels of cuckoldry in a population in Sweden. Our results demonstrate marked stability in both the genetic mating system and male alternative reproductive tactics over the breeding season. However, sneaking rates may vary geographically within a species, likely due to local selection influencing ecological factors encountered at different locations.     

Senescence and carryover effects of reproductive performance influence migration,condition, and breeding propensity in a small shorebird

Breeding propensity, the probability that an animal will attempt to breed each year, is perhaps the least understood demographic process influencing annual fecundity. Breeding propensity is ecologically complex, as associations among a variety of intrinsic and extrinsic factors may interact to affect an animal's breeding decisions. Individuals that opt not to breed can be more difficult to detect than breeders, which can (1) lead to difficulty in estimation of breeding propensity, and (2) bias other demographic parameters. We studied the effects of sex, age, and population reproductive success on the survival and breeding propensity of a migratory shorebird, the piping plover (Charadrius melodus ), nesting on the Missouri River. We used a robust design Barker model to estimate true survival and breeding propensity and found survival decreased as birds aged and did so more quickly for males than females. Monthly survival during the breeding season was lower than during migration or the nonbreeding season. Males were less likely to skip breeding (range: 1–17%) than females (range: 3–26%; β_sex = ?0.21, 95% CI: ?0.38 to ?0.21), and both sexes were less likely to return to the breeding grounds following a year of high reproductive success. Birds that returned in a year following relatively high population‐wide reproductive output were in poorer condition than following a year with lower reproductive output. Younger adult birds and females were more likely to migrate from the breeding area earlier than older birds and males; however, all birds stayed on the breeding grounds longer when nest survival was low, presumably because of renesting attempts. Piping plovers used a variety of environmental and demographic cues to inform their reproduction, employing strategies that could maximize fitness on average. Our results support the “disposable soma” theory of aging and follow with predictions from life history theory, exhibiting the intimate connections among the core ecological concepts of senescence, carryover effects, and life history.