Brachyteles Hypoxanthus Research Articles

Conservation genetics of the muriqui: past, present and future


 
 
 
 Our understanding of the genetics of the muriqui have increased in recent decades. In the mid 1980’s the first data was obtained from polymorphisms of allozymes of 10 individuals of B. hypoxanthus (northern muriqui) from Minas Gerais, and two individuals of B. arachnoides (southern muriqui) from São Paulo. All specimens were considered to be of a single species. The DNA was extracted from blood samples, which required capture and anesthesia of animals. We can now extract mitochondrial DNA from feces samples. Analyzing more than 120 individuals of the northern muriqui from two populations, we are now able make inferences about genetic variability, population distinctiveness as well as intra- and interpopulation gene flow. DNA sampling through feces is reliable, efficient, and economic, and does not risk the physical integrity of the animals, and furnishes enough DNA that is easily reproducible for PCR amplification. Using this method it is possible to sample a greater number of individuals in nature than would be possible if live capture were necessary. A muriqui feces and DNA bank has been set up, and currently has samples of 230 individuals from seven of the twelve known populations of northern muriqui. The samples resulted from field studies, but more coordinated and systematic efforts among fieldworkers at the different muriqui sites are needed to improve representation across populations and species. Future perspectives include the use of new genetic markers (nuclear and mitochondrial DNA) to identify parents, offspring, and closely related individuals in captive and wild populations; to define units for conservation and the gene flow between them; to quantify genetic variability in the populations; to assess the rate at which genetic variation has been lost over time; to estimate the degree of inbreeding in the population; and to understand better the genetic differentiation of the two species.
 
 
 

Conserving the northern muriqui in Santa Maria de Jetibá, Espírito Santo


 
 
 
 The northern muriqui is known to occur in only 12 localities, with small populations restricted to isolated forest fragments. In the state of Espírito Santo the species is currently confirmed in only three localities: in and around the Augusto Ruschi Biological Reserve; the Caparaó National Park (which extends into the state of Minas Gerais); and forests in the municipality of Santa Maria de Jetibá. We are studying the muriquis in these last two areas. Both are in the central-southern montane region of the state. In the Caparaó Natoinal Park the aim is to census the population and to estimate its social and demographic composition. The muriquis have been found in part of the 18,200 ha on the Espírito Santo side of the park, and we believe that this population is the largest in the state. In Santa Maria de Jetibá, we hope to improve the prospects for the survival of the muriquis through the following activities: 1) monitoring and managing the populations; 2) studying genetic variability and endogamy; 3) developing a conservation education program, 4) testing the potential for ecotourism; and 5) promoting actions to improve the conservation and restoration of Atlantic Forest fragments. To date, we have found 84 individuals living in 13 fragments, with subpopulations varying from 1 to about 16 individuals. We have information on their presence in another 11 fragments. We have successfully translocated one young female and are monitoring its behav- ior. The current population and genetic data suggest that we need to improve the forest connectivity in order to reduce the fragmentation and isolation of the muriqui groups. The combined efforts of scientists, government, and the local people will be fundamental to achieve this.
 
 
 

Survey and status of the muriquis (<i>Brachyteles arachnoides</i>) in the Serra dos Órgãos National Park, Rio de Janeiro


 
 
 
 The Serra dos Órgãos National Park protects 11,800 ha of Atlantic forest in the state of Rio de Janeiro (22°30'S, 43°06'W; 300 to 2,263 m above sea level). Vegetation types include montane dense evergreeen forest up to altitudes of 1,800 m; cloud forest from 1,800 to 2,000 m; and high altitude grassland above 2,000 m. This paper reports on surveys carried out in 10 localities in the park specifically to obtain a minimum estimate of the population of northern muriquis (Brachyteles arachnoides). Muriquis were sighted 26 times at altitudes ranging from 800 to 1,500 m. It is possible that they belonged to four groups in which case the minimum number of individuals recorded would be 56. If in fact the sightings were of just two groups, the minimum number of individuals would be 32. Black-horned capuchin (Cebus nigritus) and brown howler monkeys (Alouatta guariba) were also recorded for the park. The buffy-tufted-ear marmoset (Callithrix aurita) was not seen.
 
 
 

Variation in the resumption of cycling and conception by fecal androgen and estradiol levels in female Northern Muriquis (Brachyteles hypoxanthus)

We measured fecal androgen (T+DHT) and estradiol (E2) levels in female northern muriquis (Brachyteles hypoxanthus) at the Estação Biológica de Caratinga/RPPN Feliciano Miguel Abdala, Minas Gerais, Brazil, to evaluate the hormonal bases underlying individual variation in the resumption of cycling and conception. We found that androgen levels were significantly lower in females than in males, and that there were no consistent patterns in female androgen levels across precycling or cycling conditions. Females that resumed cycling earlier in the study (weeks 4-8) had higher precycling E2 levels and correspondingly lower precycling androgen/E2 ratios than females that resumed cycling later (weeks 12-16). There were no differences in female precycling androgen levels, but cycling females that conceived during or immediately after the study period had lower androgen levels and threefold higher E2 peaks than the one cycling female that failed to conceive. These results suggest that minimum E2 thresholds are necessary for both the resumption of ovarian cycling and conception. Individual variation in these components of fertility may be regulated by differences in E2 levels, which affect androgen/E2 ratios, rather than by androgen levels per se. Further research into the relative concentrations of T vs. DHT will be necessary to fully evaluate whether androgens affect cycling and conception in this species.

Age-Related Variation in Copulations of Male Northern Muriquis (Brachyteles hypoxanthus)

Age-Related Variation in Copulations of Male Northern Muriquis (Brachyteles hypoxanthus)

The near extinction of a population of northern muriquis (<i>Brachyteles hypoxanthus</i>) in Minas Gerais, Brazil

No abstract

Vocal sequential exchanges and intragroup spacing in the Northern Muriqui Brachyteles arachnoides hypoxanthus.

Sequential exchanges of vocalizations (staccatos and neighs) emitted by Northern Muriquis Brachyteles arachnoides hypoxanthus were recorded at the Biological Station of Caratinga, Minas Gerais State, Brazil. Staccatos and neighs containing larger proportion of short elements were preferentially produced during short-range exchanges; neighs, produced by a larger number of participants, were typical of long-range exchanges. Staccatos emitted by animals feeding in a dispersed manner contained a larger proportion of tonal elements than those emitted by muriquis feeding in a cohesive manner. Sequential exchanges seem thus to be constituted by two inter-related subsystems of calls that aid muriquis to coordinate intragroup spacing, despite the poor visibility of the habitat.

Hormonal changes during the mating and conception seasons of wild northern muriquis (Brachyteles arachnoides hypoxanthus).

We investigated hormonal and behavioral changes in wild male and female northern muriquis (Brachyteles arachnoides hypoxanthus) at the Estação Biológica de Caratinga, Minas Gerais, Brazil, during a 6-mo period that encompassed the onset of the 1998-1999 mating and conception seasons. Individual females resumed mating with the resumption of ovarian cycling, which was not synchronized among them or related to their cortisol levels. Females experienced two to seven cycles prior to conceiving, and the first conception occurred 2 mo after the onset of the group's mating season. There were no differences in female cortisol levels across their premating, mating, and conception conditions. Cortisol levels were significantly higher in females than in males prior to the conception season, consistent with the prediction that energy reserves may be associated with breeding readiness in females, but not males, in this species. The sustained elevation in male cortisol occurred after the peak in their sexual activity, which resulted in the first conception of the year. Male cortisol levels were positively correlated between years that were similar in rainfall, but differed in the timing of sexual and reproductive events. The timing of cortisol elevations in males appears to be generally regulated by environmental cues, but is responsive to fine-tuning by social and behavioral cues related to the unpredictable timing of reproductive opportunities within their extended mating season.

Social dynamics of male muriquis (Brachyteles arachnoides hypoxanthus)

We investigated patterns of sociality among wild male northern muriquis (Brachyteles arachnoides hypoxanthus) to explore some of the possible ways in which within-group scramble competition might shape their social and mating strategies. The 13 adult males in our study group spent an average of 54.5′4.2% of their time in proximity to at least one other adult male. They were more likely to associate with one another, but not with adult females, when they were resting than when they were feeding. Embrace rates were positively related to the proportion of time males spent in proximity during resting. Males that associated closely with one another tended to interact more often, although individual differences in male social styles and rates of interactions were apparent. Young adult males had significantly higher social maintenance rates than the oldest males in our sample, but no other effects of age were detected in any of our other behavioral comparisons. In roughly 20% of all dyads, one male valued the association significantly more than the other. Males tended to value associates with higher mating success than themselves, and to share access to the same females on the same days with their closest associates. Neither of the two pairs of maternal brothers in our study group were important associates to their kin, but brothers shared copulations in the same polyadic copulation partnerships with one another. Although still preliminary, our findings suggest that muriqui males differentiate among their possible social partners in ways that may minimize the variance in their mating success under the unusual conditions imposed by scramble competition for reproductive opportunities.

Timing of births in sympatric brown howler monkeys (Alouatta fusca clamitans) and northern muriquis (Brachyteles arachnoides hypoxanthus).

We monitored the birth patterns of sympatric brown howler monkeys (Alouatta fusca clamitans) and northern muriquis (Brachyteles arachnoides hypoxanthus) during a 4-yr period from October 1996 to August 2000 at the Estação Biológica de Caratinga, Minas Gerais, Brazil. Brown howler monkey births (n = 34) occurred throughout the year, and birth frequencies did not differ between rainy and dry season months. The aseasonal birth patterns of the howler monkeys differed significantly from the dry season concentration and dry month peak in muriqui births (n = 23). We found no effects of infant sex or the number of females on interbirth intervals (IBIs) in our 10 howler monkey study troops. IBIs of brown howler monkeys averaged 21.2 +/- 2.5 mo (n = 8, median = 21.0 mo), and were significantly shorter following dry season births than rainy season births. Their IBIs and yearling survivorship (74%) were similar to those reported for other species of howler monkeys, but yearling survivorship was much lower than that of muriquis (94%), whose IBIs were more than 12 mo longer than those of the howler monkeys. Our study extends comparative knowledge of birth patterns in Alouatta to a poorly known species, and provides insights into the different ways in which diet and life history may affect the timing of births in large-bodied platyrrhines under the same seasonal ecological conditions.