Testing artificial nestbox designs for in-situ conservation of tamarins

Abstract

Reconnecting fragmented habitats by planting forest corridors is becoming necessary to support isolated populations of threatened callitrichid primates (marmosets and tamarins) in Brazil. Tamarins frequently use tree holes as sleeping sites, but young forests do not provide these; artificial nestboxes offer a potential solution until trees in the corridors reach maturity. However, how effective such nestboxes are in attracting callitrichids and providing safety from predators is unquantified. We tested three features that might be important in the design of callitrichid nestboxes: internal shelves or entrance tunnels, to prevent predators from reaching tamarins in the boxes, and a second exit point to provide an escape route. Seven groups of zoo-housed pied tamarins (Saguinus bicolor) were given a choice between an unmodified nestbox with a single entrance and a box with one of the three test features. Each group was tested 12–13 times under each choice condition. Tamarins chose to sleep in boxes with tunnels (overall probability of selection = 0.72) and shelves (probability of selection = 0.53) in preference to unmodified boxes, but rarely opted for boxes with two entrance holes (probability = 0.3). A generalised linear mixed model showed that these differences were statistically significant (F = 15.6, df = 2, P < 0.0001). Tamarins spent more time in the hour before retiring in nestboxes with tunnels or shelves than in unmodified boxes, but less time in boxes with two entrances (F = 11.84, df = 2, 53.05, P < 0.0001). They also retired latest and rose earliest if they used boxes with two entrances. To test their susceptibility to predation, boxes of each design were baited and offered to coatis (Nasua nasua), macaques (Macaca nigra), and capuchins (Cebus capucinus and Sapajus xanthosternos). Four trials were conducted for each box type with each species. None managed to obtain bait from boxes with tunnels, but all rapidly retrieved the bait from boxes with two entrances. Pied tamarins therefore preferred nestbox designs (tunnels) offering the most protection from predators.