Early age reproduction in female savanna elephants (Loxodonta africana) after severe poaching

A 10-year study revealed that after severe poaching (>93% killed) of elephants ( Loxodonta africana ) in Zambia's North Luangwa National Park (NLNP) during the 1970s and 1980s, the age of reproduction in females was greatly reduced. Fifty-eight per cent of births were delivered by females aged 8.5–14 years, an age at which elephants were reported to be sexually immature in nearby South Luangwa National Park (SLNP) before poaching. The mean age of females at first birth (AFB) (1993, 1994) was 11.3 years. Prior to poaching, the mean age AFB in SLNP was 16 years. The NLNP age structure and sex ratio were skewed, mean family unit size was reduced, and 37% of family units contained no females older than 15 years. Twenty-eight per cent of family units were comprised entirely of a single mother and her calf, and 8% of units consisted only of orphans who would have been considered sexually immature prior to poaching. Only 6% of survivors were older than 20 years, the age at which females in little-poached populations generally become most reproductively active. After a community-based conservation programme and the UN-CITES ban on the ivory trade were introduced, no elephants were recorded killed. In spite of a high reproductive rate, 6 years after poaching decreased, the density of the NLNP population had not increased, supporting predictions that the removal of older matriarchs from family units will have serious consequences on the recovery of this species.     

Survey of the reproductive cyclicity status of Asian and African elephants in North America

The Asian and African elephant populations in North America are not self‐sustaining, and reproductive rates remain low. One problem identified from routine progestagen analyses is that some elephant females do not exhibit normal ovarian cycles. To better understand the extent of this problem, the Elephant TAG/SSP conducted a survey to determine the reproductive status of the captive population based on hormone and ultrasound evaluations. The survey response rates for facilities with Asian and African elephants were 81% and 71%, respectively, for the studbook populations, and nearly 100% for the SSP facilities. Of the elephants surveyed, 49% of Asian and 62% of African elephant females were being monitored for ovarian cyclicity via serum or urinary progestagen analyses on a weekly basis. Of these, 14% of Asian and 29% of African elephants either were not cycling at all or exhibited irregular cycles. For both species, ovarian inactivity was more prevalent in the older age categories (>30 years); however, acyclicity was found in all age groups of African elephants. Fewer elephant females (～30%) had been examined by transrectal ultrasound to assess reproductive‐tract integrity, and corresponding hormonal data were available for about three‐quarters of these females. Within this subset, most (～75%) cycling females had normal reproductive‐tract morphologies, whereas at least 70% of noncycling females exhibited some type of ovarian or uterine pathology. In summary, the survey results suggest that ovarian inactivity is a significant reproductive problem for elephants held in zoos, especially African elephants. To increase the fecundity of captive elephants, females should be bred at a young age, before reproductive pathologies occur. However, a significant number of older Asian elephants are still not being reproductively monitored. More significantly, many prime reproductive‐age (10–30 years) African females are not being monitored. This lack of information makes it difficult to determine what factors affect the reproductive health of elephants, and to develop mitigating treatments to reinitiate reproductive cyclicity. Zoo Biol 23:309–321, 2004. © 2004 Wiley‐Liss, Inc.     

Growth and age determination of African savanna elephants

Understanding the population dynamics of savanna elephants depends on estimating population parameters such as the age at first reproduction, calving interval and age-specific survival rates. The generation of these parameters, however, relies on the ability to accurately determine the age of individuals, but a reliable age estimation technique for free-ranging elephants is presently not available. Shoulder heights of elephants were measured in 10 populations in five countries across southern and eastern Africa. Data included shoulder height measurements from two populations where the age of each individual was known (i.e. Addo Elephant National Park, South Africa and Amboseli National Park, Kenya). From the known-age data, Von Bertalanffy growth functions were constructed for both male and female elephants. Savanna elephants were found to attain similar asymptotic shoulder heights in the 10 populations, while individuals in the two known-age populations grew at the same rate. The Von Bertalanffy growth curves allowed for the accurate age estimation of females up to 15 years of age and males up to 36 years of age. The results indicate that shoulder height can serve as an indicator of chronological age for elephants below 15 years of age for females and 36 years of age for males. Ages derived from these growth curves can then be used to generate age-specific population variables, which will help assess the demographic status of savanna elephant populations across Africa.     

Post-bottleneck genetic diversity of elephant populations in South Africa, revealed using microsatellite analysis

Widespread hunting had fragmented and severely reduced elephant populations in South Africa by 1900. Elephant numbers increased during the 1900s, although rates of recovery of individual populations varied. The Kruger National Park elephant population increased rapidly, to more than 6000 by 1967, with recruitment boosted by immigration from Mozambique. The Addo Elephant National Park population was reduced to 11 elephants in 1931 and remains relatively small (n = 325). Loss of genetic variation is expected to occur whenever a population goes through a bottleneck, especially when post-bottleneck recovery is slow. Variation at nine polymorphic microsatellite loci was analysed for Kruger and Addo elephants, as well as museum specimens of Addo elephants shot prior to the population bottleneck. Significantly reduced genetic variation and heterozygosity were observed in Addo in comparison to Kruger (mean alleles/locus and H(E): Addo 1.89, 0.18; Kruger 3.89, 0.44). Two alleles not present in the current Addo population were observed in the museum specimens. Addo elephants represent a genetic subset of the Kruger population, with high levels of genetic differentiation resulting from rapid genetic drift. The Kruger population is low in genetic diversity in comparison to East African elephants, confirming this population also suffered an appreciable bottleneck.     

Home range, association and related aspects of elephants in the eastern Transvaal Lowveld

Home range and association patterns of elephants Loxodonta africana in private nature reserves adjacent to the Kruger National Park, South Africa, were determined over a period of six years by using radio telemetry. The minimum convex polygon (MCP) and harmonic mean (HM) methods were used for data processing. The minimum and maximum range areas required by females were estimated at 115 and 465 km², respectively, whilst those of males varied between 157 and 342 km². Core areas of females comprised on average 10·1% of the range areas as calculated by the MCP method. Range areas between females in the Klaserie and Timbavati Private Nature Reserves differed significantly. A significant difference in range size was also found between the male population (pooled data) and the females of the Klaserie Private Nature Reserve. Range areas increased from the wet to the dry season. Three male elephant categories were established, namely males utilizing the same area during the study period, those who shifted their range areas and individuals with very large range areas which frequented the area on an irregular basis. A loose relationship existed between males. Association between females can be attributed to kinship and not to the overlapping of range areas. Results indicated avoidance behaviour between females in their core areas, which might partially explain the ability of elephants to tolerate high densities. It is concluded that male elephant hunting should be approached with caution.     

The Knysna elephants: a population study conducted using faecal DNA

The elephants of the Knysna region continue to survive, despite fears that there was only a single surviving female. Their range is larger than previously believed, and includes the Afromontane forest and mountain fynbos. The five individuals detected in this study were all females, and share a single mitochondrial DNA control region haplotype with individuals from Addo Elephant National Park. At least two of these elephants appear to be first‐order relatives, and the others may be part of a single matrilineal group. The genetic diversity detected is lower than that found in most African savanna populations, but is higher than that found at Addo, where individuals represent the descendents of a severe population size bottleneck. Levels of genetic diversity are more similar to those detected at Kruger National Park, suggesting that the Knysna elephants represent a remnant of the once widespread populations of South Africa.     

Origin and phylogeography of African savannah elephants (<Emphasis Type="Italic">Loxodonta africana</Emphasis>) in Kruger and nearby parks in southern Africa

African savannah elephants (Loxodonta africana) occur in fragmented and isolated populations across southern Africa. Transfrontier conservation efforts aim at preventing the negative effects of population fragmentation by maintaining and restoring linkages between protected areas. We sought to identify genetic linkages by comparing the elephants in Kruger National Park (South Africa) to populations in nearby countries (Botswana, Mozambique, Zambia and Zimbabwe). We used a 446 base pair mitochondrial DNA (mtDNA) control region fragment (141 individuals) and 9 nuclear DNA (nDNA) microsatellite markers (69 individuals) to investigate phylogenetic relationships and gene flow among elephant populations. The mtDNA and nDNA phylogeographic patterns were incongruent, with mtDNA patterns likely reflecting the effects of ancient female migrations, with patterns persisting due to female philopatry, and nDNA patterns likely reflecting male-mediated dispersal. Kruger elephant heterozygosity and differentiation were examined, and were not consistent with genetic isolation, a depleted gene pool or a strong founder effect. Mitochondrial DNA geographic patterns suggested that the Kruger population was founded by elephants from areas both north and south of Kruger, or has been augmented through migration from more than one geographic source. We discuss our findings in light of the need for conservation initiatives that aim at maintaining or restoring connectivity among populations. Such initiatives may provide a sustainable, self-regulating management approach for elephants in southern Africa while maintaining genetic diversity within and gene flow between Kruger and nearby regions.     

Baobabs and elephants in Kruger National Park: nowhere to hide

Baobab size class distributions were surveyed in the Limpopo National Park (LNP), Mozambique, and the Kruger National Park (KNP), South Africa. There are very few elephants in the LNP and the baobab population there had a reverse J-shaped size class distribution with many small baobabs. In contrast, the elephant-impacted baobab population of KNP displayed a mono-modal size-class distribution, with a lack in recruitment. Within KNP, elephant impact (percentage bark stripped up to the height of 3 m) decreased with increasing rockiness and slope steepness. We interpret this to suggest that steep rocky slopes are inaccessible to elephants and therefore these sites may act as a refuge for baobabs. In such inaccessible areas, the baobab population has a similar size-class distribution to that of the populations in the LNP. However, these baobab refugia are restricted in the northern KNP landscape and are therefore probably not large enough to sustain a viable baobab population.     

Comparative growth of wild male and female lions (Panthera led)

Lion growth was studied by fitting sex specific Von Bertalanffy curves and linear regressions to data on body mass, heart girth, shoulder height and vertebral column length. Measurements were recorded for 344 lions ( Panthera leo ) (158 ♂♂ and 186 ♀♀), from Kruger National Park, South Africa. Growth in mass for males and females was linear up to about 36 months of age 0 = 0–98 and 0–99 respectively). The other age-specific measurements were clearly curvilinear. Mean weights for adult lions (excluding stomach contents) were 187–5 kg (♂♂) and 124–2 kg (♀♀) respectively. Lions tended to continue growing up to about seven years in males and nine to 10 years in females after which they usually started to lose condition. Body mass and heart girth measurements of Kruger Park lions were compared with samples from three other populations. These showed that lions from East Africa were smaller than those from more southern populations in Rhodesia, Kalahari and Kruger Park.     

Population structure and behaviour of crop-raiding elephants in Kibale National Park, Uganda

We examined patterns of crop raiding by elephants across gender and age classes in relation to elephant life history and sociobiology and estimated the quantitative contribution of crops to elephant diet in Kibale National Park (KNP). Elephant dung‐boli sizes were used to estimate age and sex, while the presence of crop remains in the dung of crop‐raiding elephants was used as evidence of repeated raiding. To estimate the expected proportion of elephants raiding per age class, the age distribution of raiders was compared with the age distribution of all KNP elephants. Elephants raiding crops were predominantly males. They began raiding in expected proportions at 10–14 years while a higher than expected proportion raided crops at 20–24 years. These results suggest that crop raiding is initiated at an age when male elephants leave their families and a large proportion of elephants raid when they are approaching reproductive competition. Evidence from dung of crop raiders, suggests that repeated raiding increases with age. Crop raiders derived 38% of their daily forage from the short time spent raiding, consistent with expectations of foraging theory. Males may be more likely to learn crop raiding because they are socially more independent and experience intense mating competition than females.     

Dynamics of social and energetic stress in wild female chimpanzees

Stress hormone measurements can reinforce and refine hypotheses about the costs of particular contexts or behaviors in wild animals. For social species, this is complicated because potential stressors may come from the physical environment, social environment, or some combination of both, while the stress response itself is generalized. Here, we present a multivariate examination of urinary cortisol dynamics over 6 years in the lives of wild female chimpanzees in the Kanyawara community of Kibale National Park, Uganda. We hypothesized that chimpanzee socioecology provides strong indications of both energetic and social stress to females, but that the salience of these stressors might vary over a female's life history in accordance with their changing reproductive costs and social interactions. Using linear mixed models, we found that urinary cortisol levels increased significantly with age but were also elevated in young immigrants to the community. Across reproductive states, cycling, non-estrous females had relatively low cortisol compared to lactating, estrous, or pregnant females. Aggression from males led to higher cortisol levels among estrous females, frequent targets of aggressive sexual coercion. In contrast, energetic stress was most salient to lactating females, who experienced higher cortisol during months of low fruit consumption. Low dominance rank was associated with increased cortisol, particularly during the energetically demanding period of lactation. The effects of female conflict were felt widely, even among those who were the primary aggressors, providing further evidence that long-term resource competition, while apparently muted, exerts a far-reaching impact on the lives of chimpanzee females.     

Reproductive seasonality in the Indian pygmy field mouse,Mus terricolor

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

Spawning related movement of shovelnose sturgeon in the Missouri River above Fort Peck Reservoir,Montana

The hypotheses of this study were (i) that shovelnose sturgeon would make upstream movements to spawn, (ii) movement of spawning fish would be greater in a year with higher discharge, and (iii) that spawning fish would have greater movements than reproductively inactive fish. Shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820) in five reproductive categories (e.g. males, confirmed spawning females, potentially spawning females, atretic females, and reproductively inactive females) were tracked in 2008 and 2009. All reproductive categories, except reproductively inactive females, exhibited large‐scale movements and had omnidirectional movements. No differences in movement rates were observed in confirmed spawning females between years despite a 45% higher peak discharge in 2008 (839 m³ s^?1) than in 2009 (578 m³ s^?1). A peak discharge was obtained at a faster rate in 2008 (165 m³ s^?1 day^?1) than in 2009 (39 m³ s^?1 day^?1), and high discharge was of greater duration in 2008. Reproductively inactive females did not exhibit large‐scale movements and their movement rate differed from other reproductive categories. Shovelnose sturgeon spawned in both years, despite highly varying hydrographs between years.     

Age determination by back length for African savanna elephants: extending age assessment techniques for aerial-based surveys

Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables.     

Bioenergetics and phenology of reproduction of the introduced red swamp crayfish, Procambarus clarkii, in Do·ana National Park, Spain, and implications for species management

1. The red swamp crayfish, Procambarus clarkii (Girard), is a North American species which was introduced into the Lower Guadalquivir, Spain, in 1974. Procambarus clarkii has become a key species since it has greatly altered the functioning and structure of the ecosystems it has invaded.
2. Since P. clarkii spawn spontaneously throughout the year, it is to be expected that their ecological impact on the ecosystem may vary depending of the timing of habitat flooding (e.g. temporary freshwater marsh, and temporary or permanent pond). The objective of the present study was to understand the reproductive phenology and bioenergetics of P. clarkii in Do·ana National Park, Spain, freshwater ecosystems, and consequently, propose some management plans for their populations.
3. Five stages of ovarian development were detected. Final ovarian maturation occurred a few days before spawning and spawning was synchronized among mature females of all populations. Egg numbers hatched in pleopods ranged from 450 to 550. Timing of juvenile release from pleopods varied greatly (10–35 days).
4. Gravid females support most of their metabolic needs by catabolizing carbohydrates (overall mean of O:N = 30.39), and to a lesser extent, lipids. The aerobic and excretory metabolisms of gravid females were lower than those of immature animals of similar weight.
5. Analysis suggested that several factors influence the spawning of crayfish at the monitored sites. The major factors are water regime and temperature. Red swamp crayfish appear to be a spontaneous spawning species which may adjust their reproductive cycle to the timing of flooding, enhancing the utilization of available resources.
6. Populations of P. clarkii in Do·ana National Park could be controlled by the management of the water regime and by devising a fishing scheme which would maintain an appropriate population structure.     

Mating behavior and endocrine profiles of wild black and white Colobus monkeys (Colobus guereza): toward an understanding of their life history and mating system

Black and white colobus monkeys (Colobus guereza, "guerezas") show no external signs of estrus, and little is known about their mating behavior or reproductive endocrinology. To learn more about the life history characteristics and mating system of guerezas, we documented the mating behavior and ovarian hormone profiles of 10 cycling, lactating, and pregnant females in a wild population. We studied six groups of guerezas in Kibale National Park, Uganda, and collected ad libitum data on their mating behavior. We collected urine samples every 1.9+/-0.2 days from potentially fertile females and quantified conjugated urinary estrogen (E1S) and progesterone (PdG) metabolites using enzyme immunoassay (EIA). Females solicited 50.5% of copulations, and most copulations occurred during the interval starting 5 days before presumptive ovulation and ending 2-3 days later, with the highest copulatory levels occurring close to ovulation. We show that the median ovarian cycle length is 24 days, the median gestation length is approximately 158 days, the length of lactational amenorrhea is at least 7-8 months, and the median interbirth interval for females with surviving infants is approximately 22 months. We also document overlap between females' receptive periods in one-male, two- to three-female groups, which may mean that male transfer into such groups is potentially profitable.     

Patterns of behavior across reproductive states of free-ranging female black-handed spider monkeys (Ateles geoffroyi)

Reports on the behavior of spider monkeys (genus Ateles) describe a suite of 5-6 behaviors that are indicative of an estrous female. This study presents hormonal data as an independent measure of reproductive state to determine if these behaviors are associated with any particular reproductive state or stage of the ovarian cycle. Fecal samples collected from 6 free-ranging female black-handed spider monkeys (Ateles geoffroyi) over the course of 11 months were assayed for estrogen (E1C) and progesterone (PdG) metabolites, using an enzyme immunoassay. Behavioral data collected from the same females were analyzed for patterns associated with different reproductive states. A more detailed analysis of behavioral data associated with reproductively cycling periods determined whether each behavior clustered with copulations or a particular phase in the ovarian cycle. Observations of place-sniffing were more frequent for 4 of 5 females when reproductively cycling. Of all copulations observed, 80% occurred when the female participant was reproductively cycling. In addition, the rates of self-clitoral hold and self-clitoral rub behaviors were significantly higher for 2 of 4 and 4 of 5 of females, respectively, when reproductively cycling. No behavior consistently occurred in association with copulations or with any particular phase in the ovarian cycle. Results from this study suggest that the behaviors tested in this paper can provide some information regarding female spider monkey reproductive state (whether or not she is reproductively cycling), but that they are not indicators of estrus in female spider monkeys.     

Reproductive biology and postnatal development in the tent-making bat Artibeus watsoni (Chiroptera: Phyllostomidae)

In this study we investigated the reproductive patterns and postnatal development in the tent-making bat Artibeus watsoni . We sampled two populations in the Golfito Wildlife Refuge and Corcovado National Park, south-western Costa Rica, from June 2003 to March 2005. Most females were pregnant during the months of January and June, and most were lactating in March and July, indicating that this species exhibits seasonal bimodal polyoestry, with the first parturition peak occurring in February–March and the second in June–July. Additionally, we observed a postpartum oestrus following the first parturition, but not after the second. Females entered oestrus again in November–December and had a gestation period of c . 3 months. A female-biased sex ratio of neonates was observed during the second parturition period, and young were born at 32 and 56% of their mothers' body mass and length of forearm, respectively. Adult proportions in length of forearm were attained faster than adult proportions in body mass, and sustained flight was only possible after 35 days of age, when pups had achieved 100 and 80% of adult length of forearm and body mass proportions, respectively. Weaning and roosting independence occurred when young were c . 30–40 days old, and young females appeared to remain close to their place of birth, at least for their first mating period, whereas adult males were never recaptured near their birth site. In addition, sexual maturity was reached in as little as 3 months in females born during the first parturition period, whereas females born during the second birth period in June–July seemed to reach maturity at 6 months of age. Our results show that A. watsoni belongs to the faster lane of the slow–fast continuum of life-history variation in bats, which may be attributed primarily to its roosting and feeding ecology.     

Results of the third reproductive assessment survey of North American Asian (Elephas maximus) and African (Loxodonta africana) female elephants

A written survey assessed reproductive status of female Asian and African elephants in AZA/SSP facilities in 2008, and data were compared to surveys conducted in 2002 and 2005. Results showed that ovarian acyclicity rates across the surveys remained unchanged for Asian (13.3, 10.9 and 11.1%) and African (22.1, 31.2 and 30.5%) elephants, respectively (P > 0.05), but were higher overall for African compared to Asian elephants (P < 0.05). In 2008, the percentages of Asian and African elephants with irregular cycles (14.3 and 15.8%) and irregular + no cycles (25.4 and 46.4%) was similar to 2005 (7.6 and 11.8%; 18.5 and 43.0%), but were increased compared to 2002 (2.6 and 5.2%; 16.0 and 27.3%), respectively (P < 0.05). For both species, ovarian acyclicity increased with age (P < 0.05). Reproductive tract pathologies did not account for the majority of acyclicity, although rates were higher in noncycling females (P < 0.05). Bull presence was associated with increased cyclicity rates (P < 0.05) for Asian (92.5 vs. 58.3%) and African (64.9 vs. 57.8%) elephants compared to females at facilities with no male, respectively. Cyclicity rates were higher for Asian (86.8 vs. 65.2%) and African (67.9 vs. 56.7%) elephants managed in free compared to protected contact programs (P < 0.05), respectively. Geographical facility location had no effect on cyclicity (P > 0.05). In summary, incidence of ovarian cycle problems continues to predominantly affect African elephants. Although percentages of acyclicity did not increase between 2005 and 2008, 42.2% Asian and 30.2% African females were no longer being hormonally monitored; thus, reproductive cycle abnormalities could be worse than current data suggest.     

Mahale chimpanzees: grouping patterns and cycling females

The social system of chimpanzees (Pan troglodytes schweinfurthii) is characterized by the fission-fusion of social groups. Several studies have reported that females are less gregarious than males. In the current study, adult female gregariousness depended on their reproductive state. Noncycling adult females (pregnant, lactating, or post reproductive) were observed in large bisexual parties less often than cycling adult females. On the other hand, cycling adult females were observed in large bisexual parties as often as males, regardless of their estrous state. More males were in parties that included cycling adult females with maximal genital swelling (estrous females) than in parties without them. Moreover, a bisexual party including more estrous females contained more males. These results suggest that large bisexual parties of chimpanzees are constructed by a dual mechanism. First, cycling adult females are attracted to parties that consist of the top ranking male and large numbers of adult and adolescent males. Second, adult and adolescent males that did not belong to parties originally are attracted by estrous females and join them. Thus, in Mahale Mountains National Park, Tanzania, bisexual parties of chimpanzees can be characterized as "parties for reproduction."