Fernando Peláez

Distribution and Habitat Associations of Baboons (Papio hamadryas) in Central Eritrea

At least three diurnal primate taxa are still present in Eritrea, NE Africa: hamadryas baboons (Papio hamadryas hamadryas), olive baboons (Papio h. anubis) and grivet monkeys (Chlorocebus aethiops aethiops). However, information on status and distribution of primates and their habitats in Eritrea is outdated and incomplete. We conducted a primate survey, focussing on hamadryas baboons, to obtain data which will be integrated in a national wildlife management and conservation plan in Eritrea. We obtained information about the geographical distribution and abundance of baboons, their altitudinal range, habitat quality of their home-ranges, aggregation sizes at sleeping cliffs and predator presence. We described habitat quality via the Normalized Difference Vegetation Index (NDVI), a vegetation classification of Landsat MSS satellite data. Hamadryas and olive baboons are still present in Eritrea in ample numbers. Their geographical distributions in 1997 and 1998 did not deviate significantly from their historical distributions. An estimated 15,000 Papio hamadryas hamadryas lived in the 25,000-km2 area of survey (0.58 baboons/km2). Population densities of hamadryas baboons in many parts of the survey area are higher than at Kummers (1968) study site in Ethiopia. Hamadryas baboons live at all altitudes in four of five ecogeographical zones of Eritrea. Olive baboons replaced them in the western lowlands. Both baboon taxa tend to select better quality habitats, characterized by a higher normalized difference vegetation index (NDVI) than the average for the respective ecogeographical zones. Hamadryas baboons show a greater ecological plasticity than olive baboons, which are confined to riverbeds with extended gallery forest. By the end of 1999, a hybrid zone could not be confirmed.

Mate choice differences according to sex and age

We used 7,415 advertisements published in Spain to analyze traits sought/offered by men and women from different age groups. Findings regarding age, socioeconomic status, and physical attractiveness requirements support evolutionary predictions about mate preferences. However, changes in trait preferences among women under 40 appear to be contingent on Spain’s socioeconomic transformation. Women under 40 seek mainly physical attractiveness in men, whereas those over 40 seek mainly socioeconomic status. The trait most sought by men in all age groups is physical attractiveness. Traits sought and offered by advertisers may be conditioned by the personal situation of the advertiser. Mean age of advertisers (around their forties) and Spain’s social indicators suggest that the majority of advertisers have been unsuccessful in the mating arena at the conventional age.

Group Composition and Adult Sex-ratio of Hamadryas Baboons (Papio hamadryas hamadryas) in Central Eritrea

During a survey of the geographical distribution and abundance of hamadryas baboons (Papio hamadryas hamadryas) in central Eritrea, we collected detailed demographic data on six bands at four sites in different ecogeographical zones. The proportions of age-sex classes within the six bands differed only with respect to juveniles. The general social organization of the Eritrean hamadryas baboons is similar to that reported for Ethiopia and Saudi Arabia. Eritrean hamadryas baboons live in a nested fission-fusion system, with one-male units as the basic social entity. Although the baboons were not provisioned, as they are in many places in Saudi Arabia, and habitat quality in Eritrea is lower than that in Ethiopia, sex-ratios and group composition corresponded more to those found in the Saudi Arabian population. Sex-ratios within the study population, in bands and also in one-male units were significantly more female-biased than in Ethiopian ones, and one-male units tended to be larger. Data from Eritrea suggest that these differences are due to a combination of a heavily fluctuating rainfall pattern and differential maturation of the sexes.

Greeting movements among adult males in a colony of baboons:Papio hamadryas, P. cynocephalus and their hybrids

Seven greeting movements performed by four adult males belonging to a colony of baboons (Papio hamadryas, P. cynocephalus and their hybrids) were described.The hamadryas male has more number and more refined repertoire of movements than the yellow baboons, what would mean that the greeting movements possess a species-specific nature. This characteristic is expressed also by the existence of some inappropriate responses of the yellow baboons to the greeting of the hamadryas male. The differences in the greeting movements between both species would be explained as characteristic consequences of their social system organization. The hybrid male, having acquired a system organization similar to that of the hamadryas male, has acquired the same signal code, too, according to this system.The hybridization tendency would be adaptive in those colonies or troops with mixed species.

Verreaux's eagles (Aquila verreauxi) as potential predators of hamadryas baboons (Papio hamadryas hamadryas) in Eritrea.

In this paper we describe for the first time encounters of Verreauxs eagle (Aquila verreauxi) with hamadryas baboons (Papio hamadryas hamadryas) in the central highlands of Eritrea (15° 22′ N, 38° 58′ E, 2300 m). During 12 h of observation on 4 days, we observed four encounters of Verreauxs eagles with baboons, of which three can be classified as possible attacks. The baboons always responded with alarm calls. In three cases some immatures rushed to adult group members and clung to them, particularly to the adult male. Adult males threatened the eagle, and the whole group did not flee. The response of baboons towards smaller raptors like tawny eagles (Aquila rapax) and black kites (Milvus migrans) was very different. The adult baboons gave no alarm barks but scanned the raptors. The permanent presence of a pair of Verreauxs eagles in the home range of the baboons may represent a considerable predation pressure, at least for immature baboons. Am. J. Primatol. 47:61–66, 1999.

Feeding tactics in juvenile rhesus monkeys (Macaca mulatta).

In a group of rhesus monkeys, feeding tactics of juveniles were studied in a competitive situation in which food presentation had been modified, and where food was supplied in a feeding trough six times a day. Juvenile offspring of high‐ranking mothers remained longer in the feeding area gathering food. In contrast, juvenile offspring of low‐ranking mothers went less often to the feeding area, primarily to collect food. Low‐ranking juveniles also gathered the food faster than did dominants and used longer feeding bouts. High‐ranking juveniles interrupted their feeding more spontaneously than did subordinate ones. Low‐ranking juveniles did so more often as a result of avoiding and being startled. Juvenile males entered the feeding area to satisfy their food requirements more often than females, but were also aggressively expelled more than females. No relation was found between age in months of juveniles and any feeding parameters or causes of interruption. Nor were significant differences found between young and old juveniles. Juvenile rhesus appear to use different tactics in accessing food according to their sex and to their mothers’ dominance rank. Am. J. Primatol. 51:147–152, 2000.

Reconciliation in captive cotton-top tamarins (Saguinus oedipus), a cooperative breeding primate.

Reconciliation has been demonstrated in all primate species in which the phenomenon has been studied. However, reconciliation has been studied in only two species of callitrichids, and conclusions remain controversial. The first aim of this study has been to find out whether captive cotton‐top tamarins (Saguinus oedipus) reconcile, since this is the first such study on this species. We examined 227 conflicts in three family groups (N=19). Instances in which individuals remained together in t=0 (29; 12.8%) were not analyzed. The cotton‐top tamarins showed heightened affiliation between opponents in the postconflict periods (PC) compared with matched control (MC) periods (39.88±5.12% and 3.18±1.27%, respectively), with a corrected conciliatory tendency of 37.17±5.37%, and a “time window” that included the first 180 sec of the PC period. Former opponents were the most likely recipient of affiliative behaviors during the PC periods: 39.83±4.26% vs. 11.36±5.33% during MC periods. The proportion of attracted pairs (47.13±6.25%) was significantly higher than those of dispersed pairs for male–male conflicts (3.79±1.79), but not for male–female conflicts (27.31±9.32 and 4.82±2.9, respectively). In cooperative‐breeding species, specific sex‐class dyads might differ in how they resolve conflicts. Am. J. Primatol. 71:895–900, 2009.

The Equivocal Relationship Between Territoriality and Scent Marking in Wild Saddleback Tamarins (Saguinus fuscicollis).

Researchers have often assumed that scent marking serves a territorial function in callitrichines, although some controversy exists. To fulfill such a function, scent marks should 1) prevent intrusions, 2) ensure access to feeding resources, 3) enable avoidance of intergroup encounters, or 4) play an important role in the aggressive encounters between groups. We studied 13 saddleback tamarins (Saguinus fuscicollis) belonging to 3 free-ranging groups, which formed mixed-species troops with moustached tamarins (S. mystax) in the Amazonian rain forest of Peru. None of the predictions were confirmed. The tamarins used a border-marking strategy, marking more on the periphery of their territory. However, feeding trees in overlap and encounter areas received more scent marking but were still visited by neighboring groups. Intergroup encounters occurred more often than expected, and scent-marking frequency was not higher during them than when no other group was present. It appears that instead of defending a territory in the classic sense, the tamarins are optimizing signal transmission by depositing their scents where the probability of detection by neighbors is higher. Saddleback tamarins may use shared areas of their home ranges to exchange information with neighboring groups, perhaps regarding reproductive opportunities.

Changes in Body Mass of Expectant Male Cotton-Top Tamarins (Saguinus oedipus)

It has been noted that expectant cotton-top tamarin males in captivity experience a body mass increase during the last months of their mates’ pregnancies, and this has been explained as being a male physiological response. We studied the body mass of 4 inexperienced and 4 experienced expectant males, and we expected to observe a larger body mass increase among the experienced ones since they undergo multiple hormonal changes in comparison to inexperienced expectant males. However, while inexperienced expectant males gained body mass during months 4–6 of the pregnancy period by a mean ±SD of 5.4 ± 3.1% (i.e. 29 ± 17 g), the experienced ones did not (mean ± SD of months 4–6, 0.5 ± 1.7%, i.e. 5 ± 12 g). The results suggest that other factors, such as behavioural communication between pairs and feeding and resting behaviour, should be studied in order to clarify the basis of this body mass increase.

Can Overmarking Be Considered as a Means of Chemical Mate Guarding in a Wild Callitrichid

Mate guarding is a male strategy to monopolize matings and thus to ensure paternity. Since in callitrichids female reproductive status is advertised by scent marks, one may expect mate guarding by chemical means. We addressed this question during an episode of consortship observed in a polyandrous trio of wild saddleback tamarins (Saguinus fuscicollis). During consortship, the consort male was the only one to allomark the female. Scent marking frequency decreased for all individuals, although the consort male marked more than the other male during consortship, while there was no difference in the previous period. During consortship, almost 50% of female scents were overmarked by the consort, and more than 56% of the consort’s scent marks were employed to overmark the female’s scents. Therefore, the other male had limited access to female scent marks. Mate guarding may thus have a chemical component in tamarins, and olfactory communication may play an important role in mating competition.