The effect of social and ecological factors on the time budget of wild vervet monkeys

Animals often have a limited time to perform different fitness‐enhancing activities, such as the trade‐off between socializing versus foraging in group‐living species. Many previous studies have focused on how ecological and social factors influence activity budget at the individual or group level in various species. However, few primate studies have focused on multiple study groups living within a similar habitat. Here, we analyse group, season and sex effects on the individual activity budget of wild vervet monkeys (Chlorocebus pygerythrus) living in four groups with overlapping home ranges. Generally, our findings support previous studies on primates. Our results indicate that intragroup competition may force larger groups to spend more time feeding and less time resting. We also found that seasonal variation, and therefore food availability, has a strong influence on the monkeys’ activity budget. Females, which are the philopatric sex in vervet monkeys, spent more time socializing while, in general, males spent more time resting. However, we did not find any difference on the time spent socializing between groups. Since there is evidence that not only time constraints and habitat quality but also group size influence individual behaviours and ultimately group living, we advise that future studies should focus on multiple groups of the same species living in the same habitat in order to better understand how all these variables are interlinked.     

Grunt to go—Vocal coordination of group movements in redfronted lemurs

To remain cohesive as a group, individuals must coordinate their movements between resources. In many species, vocalisations are used in this context. While some species have specific movement calls, others use calls which are also employed in different contexts. The use of such multicontextual calls has rarely been studied quantitatively, especially during both the pre‐departure and departure period associated with collective decisions. We thus investigated the use of close calls (“grunts”) for the coordination of collective movements in four groups of wild redfronted lemurs (Eulemur rufifrons) in Kirindy Forest, Western Madagascar. Group movements are started by an initiator, who moves away from the group and is joined by followers setting out in the same direction. We observed collective movements and recorded vocalisations from 18 focal individuals (54 movements recorded for followers, 21 for initiators). The grunt rate of both initiators and followers was higher in the pre‐departure period than in a control context (i.e., during foraging). Initiators of collective movements grunted more often than followers in the pre‐departure period as well as at individual departure. The latter difference was due to the initiators’ grunt rates increasing earlier than the followers’ and remaining at an elevated level for longer. These observations suggest that grunts serve to coordinate the departure by indicating the individual's readiness to move. The pre‐departure period, in which both initiators and followers showed an elevated grunt rate, may provide the basis for a shared decision on departure time. The difference in initiator and follower call rates suggests that grunts may have a recruitment function, but playback experiments are required to test this potential function. Overall, our study describes how multicontextual close calls can function as movement calls, with changes in call rate providing a potential feedback mechanism for the timing of group movements. This study thus contributes to a more detailed understanding of the mechanisms of group coordination and collective decision‐making.     

New remains of Diplocynodon (Crocodylia: Diplocynodontidae) from the Early Miocene of the Iberian Peninsula

We describe crocodylian remains from the Early Miocene (MN4) site of Els Casots (Subirats, Vallès-Penedès Basin, NE of the Iberian Peninsula). Referral to Diplocynodon (Alligatoroidea: Diplocynodontidae) is justified by several cranial and postcranial features, including: (1) the subequal and confluent alveoli of the maxilla (fourth and fifth) and dentary (third and fourth); (2) the position of the foramen aëreum on the quadrate; (3) the small and ventrally reflected medial hemicondyle of the quadrate; (4) the distinct dorsoventral step on the frontal; and (5) the bipartite ventral osteoderms. Multiple morphological features are consistent with an attribution to Diplocynodon ratelii, previously known from the Early Miocene (MN2) of France, and discount an alternative attribution to other species of the genus, including Diplocynodon ungeri from the Middle Miocene (MN5) of Austria. The described material from Els Casots is smaller in size than the French material of D. ratelii, possibly reflecting an earlier ontogenetic stage. The described remains constitute the first report of D. ratelii and the youngest record of Diplocynodon in the Iberian Peninsula, where only Diplocynodon muelleri and Diplocynodon tormis have been previously reported. The presence of Diplocynodon further supports the lacustrine depositional environment previously inferred for Els Casots and also indicates a relatively high temperature.     

Species-specific albumin in fossil bones from Orce, Granada, Spain

A skull fragment (VM-0) from Orce, Granada, Spain, dated palaeomagnetically at about 1.6 Myr, is thought by some palaeontologist to be hominid, while others maintain it is equid. If hominid, it would be by far the oldest evidence ofHomo in Europe. Immunological studies on residual albumin in this fossil were carried out independently, and with different immunological methods, at the University of California, San Francisco (radioimmunoassay), and at the University of Granada, Spain (enzyme immunoassay). Other fossils attributed to hominids also studied wereVM1960 from Venta Micena, andCV-1 from Cueva Victoria, Murcia, Spain. Undisputed equid and bovid fossils from the same deposits and dated to a similar period as the Orce skull were also analyzed. Our results showed that species-specific albumin can be detected in 1.6 Myr-old hominid, equid and bovid fossils. The albumin from the Orce skull fragment and fromVM-1960 was immunologically closer to human albumin. These findings support the contention that theVM-0 andVM-1960 are hominid and that members of the genusHomo occupied southern Spain 1.6 Myr ago.     

Primate Community Dynamics in Old Growth Forest over 23.5 Years at Ngogo,Kibale National Park,Uganda: Implications for Conservation and Census Methods

Few data exist regarding long-term changes in primate populations in old-growth, tropical forests. In the absence of this information, it is unclear how to assess population trends efficiently and economically. We addressed these problems by conducting line-transect censuses 23.5 years apart at the Ngogo study area in Kibale National Park, Uganda. We conducted additional censuses over short time intervals to determine the degree to which the temporal distribution of censuses affected estimates of primate numbers. Results indicate that two species, blue monkeys and red colobus, may have experienced significant reductions over the past 23.5 years at Ngogo. In contrast, five other species, baboons, black-and-white colobus, chimpanzees, mangabeys, and red-tailed guenons, have not changed in relative abundance. Additional findings indicate that different observers may vary significantly in their estimates of sighting distances of animals during censuses, thus rendering the use of measures of absolute densities problematic. Moreover, censuses conducted over short periods produce biased estimates of primate numbers. These results provide guidelines for the use of line-transect censuses and underscore the importance of protecting large blocks of forests for primate conservation.     

Studies on transmission of hepatitis A virus to squirrel monkeys

Non-human primates have been playing an essential role in the study of hepatitis A virus (HAV) biology, pathogenesis and for testing candidate HAV vaccines. This study was to determine the suitability of squirrel monkeys (Saimiri sciureus) as animal model for HAV infection. Animals were inoculated, either intragastrically or intravenously, with a Brazilian HAV isolate (HAF-203). Alanine aminotransferase (ALT) and anti-HAV antibodies (IgM and total) were monitored. Feces were daily collected for HAV antigen and HAV RNA detection. Samples of liver tissue were obtained by biopsy before inoculation at peak ALT levels and/or when anti-HAV antibodies developed, and at necropsy for morphological examination. Monkeys inoculated by the intravenous route rapidly developed significant elevations of serum ALT, anti-HAV antibodies, and liver histologic changes, while the only evidence of HAV infection in intragastrically inoculated animals was the seroconversion. Moreover, squirrel monkeys excreted very low levels of HAV detectable in only few fecal samples after amplification by RT-PCR, different from humans and other non-human primate species that eliminate large quantities of virus during the late incubation period. The unusual onset of hepatitis A in experimentally infected squirrel monkeys represent an important obstacle for its use as animal model for the study of this viral infection. However, they can represent a valuable tool for the obtention of hyperimmune sera for HAV, in the view of the very high titer of anti-HAV developed (10⁵) 24 days after a single intravenous inoculation.     

灵长类动物的食物分享行为

食物分享是灵长类动物的一种重要社会交往行为,主要发生在成体-幼体间和成体-成体之间。本文从这两个方面对灵长类动物食物分享的行为表现、特点以及功能进行总结,着重比较了无亲缘关系的成年个体间食物分享的互惠解释和骚扰解释。通过对以上内容的综合分析,进一步提出了食物分享行为的未来研究方向以及对人类合作行为演化的启示。