# Behavioral Adjustments by a Small Neotropical Primate (Callithrix jacchus) in a Semiarid Caatinga Environment

Authors: María Fernanda Castellón De la Fuente; Antonio Souto; Marilian Boachá Sampaio; Nicola Schiel
Journal: The Scientific World Journal
 (2014)

Leave sleeping site
Sunset
*
Return to sleeping site
Group  A
Group B
Nov.
4:57
5:07
17:27
17:14
4
5
Dec.
5:03
5:14
17:36
17:11
2
4
Jan.
5:23
5:24
17:51
17:31
3
3
Feb.
5:29
5:31
17:48
17:24
4
3
Mar.
5:29
5:33
17:34
17:29
3
4
Apr.
5:27
5:31
17:21
17:19
2
3
Mean
5:18
5:23
17:36
17:21
3
3.7
*Source: http://euler.on.br/ephemeris/index.php.


## 4. Discussion

Our findings show that common marmosets inhabiting the Caatinga adjusted their behavioral patterns to adapt to the high temperatures and apparent resource scarcity that characterize this environment. We base this assumption on the changes in behaviors such as resting, foraging, gum feeding, and locomotion that were observed with temperature fluctuations. Our results were comparable to those found in other primates living in similar environmental conditions (baboons: [27, 28]; vervet monkeys: [36]).In our study, an association between temperature and resting was obtained throughout the day. These results complement each other and reinforce the importance of resting as a behavioral mechanism to avoid the risk of thermal stress (e.g., [28, 32]). While resting bouts in common marmosets at our study site occurred predominantly from 10 am to 2 pm, the same bouts were displayed in a much shorter interval (two hours) in the Atlantic Forest sites ([7, 8, 51]: 11 am–1 pm). Moreover, daily sleeping cycles also appeared to be longer in the Caatinga; that is, common marmosets left their sleeping site just five minutes after sunrise and returned to sleep only 15 minutes before sunset. These values are strikingly shorter when compared to those obtained in the Atlantic Forest conditions: 30 min after sunrise and the same length before sunset (e.g., [7, 8]). This behavior in the Caatinga might be a possible strategy to avoid the increase in body temperature, as the 10 am to 2 pm heat appears to reduce the frequency of locomotion and foraging activities.In contrast to resting, which was displayed more frequently into the midday period (i.e., temperature becoming increasingly hot), foraging did not follow such a pattern. Instead, it maintained a level of occurrence up to ~10 am (~31°C) and then sharply decreased. As observed in vervet monkeys [36] in semiarid riparian woodlands, this result suggests that the Caatinga environment forces the small common marmosets to maintain the search for food for as long as they can thermally tolerate. To strengthen the idea of how important it is to obtain food in the Caatinga, locomotion was progressively reduced as temperature increased, whereas foraging did not decrease. That is, as the task of locomotion requires more physical effort from the common marmosets as temperature increased, they reduced this behavior however continued to search for food up to a certain point.The need to compensate food scarcity also appeared to interfere in gummivory. Throughout the day, our study groups devoted an extensive period of time (up to 8 am) to this activity, especially during the morning hours. This also contrasts with data from Atlantic Forest sites (e.g., [8]: ~6 am to 7 am; ~4 pm to 5 pm). Such contrast suggests a high dependence on plant exudates by common marmosets living in the Caatinga, as gum is a readily available resource throughout the year. Amora et al. [19] observed that instead of relying mainly on gum exploitation, marmosets in the Caatinga used alternative food items such as leaves. This strategy was not observed during our study. Their diet consisted mainly of gum, fruits, arthropods, and small vertebrates, similar to the Atlantic Forest common marmosets [13]. It is still unclear how common marmosets adjust their diet toward food scarcity, and thus further studies need to be conducted in the Caatinga habitat.Gummivory behavior byC. jacchusis also associated with the size of their home range [52]. In the home range of our study group, sizes were within the variation described for the Atlantic Forest ([51]: 2–5 ha; [53]: 0.72–1.62 ha; [7]: 0.5–3 ha; [8]: 4.98 ha; [54]: 2.5–6.5 ha; [55]: 4.11 ha). Apparently, the harsh condition such as in the Caatinga did not lead to a larger home range as we expected. The cost to explore a larger home range under high temperatures in such environment may exceed its benefits. However, intergroup encounters seemed to influence the home range size [54]. Thus, the smaller home range of group A might be explained, as this group had intergroup encounters with neighboring groups. By contrast, group B did not have any conflicts with other groups, which might have given them more freedom of movement to explore a larger area.Finally, up to seven sleeping sites per group were used during our study period (6 months), and each site was not used more than three nights in a row. Previous reports on the number of sleeping sites in the Atlantic Forest areas vary considerably (e.g., [8]: n
=
15 (11 months); [56]: n
=
5 (10 months); [57]: n
=
2 (20 months); [7]: n
=
1
–
4 (4 months)). Sleeping sites in the Atlantic Forest are usually located in tall trees with a closed canopy [51, 57] and are near immediate sources of food such as gum [56]. In general, sleeping sites are selected to provide overall comfort and safety [58–62]. During our study period, sleeping sites were located in more open canopies. Nevertheless, animals chose to sleep nearby or even in the gum tree itself.


## 5. Conclusion

Overall, common marmosets inhabiting the Caatinga exhibited a number of behavioral adjustments toward temperature fluctuations. The extended period in which they display resting bouts particularly expresses the effect that high temperatures can have on this small primate. It is clear that the survival ability of these small primates in such a challenging environment can only be fully understood when the behavioral dimensions are taken into account. Our findings can help us better understand how common marmosets became one of the most successful primates, as well as how they colonize remarkably different environments such as the Caatinga and the Atlantic Forest.



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*Source: 326524-2014-11-06.xml*