João M Silla

Bio: João M Silla is an academic researcher. The author has contributed to research in topics: Predation & Leucopternis. The author has an hindex of 1, co-authored 1 publications receiving 13 citations.

Run, hide, or fight: anti-predation strategies in endangered red-nosed cuxiú (Chiropotes albinasus, Pitheciidae) in southeastern Amazonia.

Abstract: Although primate predation is rarely observed, a series of primate anti-predation strategies have been described. Energetic costs of such strategies can vary from high-cost mobbing, via less costly alarm calling, to low-cost furtive concealment. Here we report the anti-predation strategies of red-nosed cuxiu, Chiropotes albinasus, based on direct observations from four study sites in southeastern Brazilian Amazonia. Over a collective period of 1255 fieldwork hours, we observed nine direct interactions between raptors (all potential predators) and red-nosed cuxius. Of these, one (11%) resulted in predation. Raptors involved were: Harpia harpyja (four events), Leucopternis sp. (two events), Spizaetus tyrannus (one event), and unidentified large raptors (two events). Predation attempts occurred in flooded-forest and terra firme rainforest, were directed at both adult and non-adult cuxius, and involved both adult and juvenile raptors. Anti-predation strategies adopted by the cuxius included: (1) group defence and mobbing behaviour (two occasions), (2) dropping into dense sub-canopy (seven occasions), (3) alarm calling (eight occasions), and (4) fleeing to, and hiding in, dense vegetation (eight occasions). During each encounter at least two of these behaviours were recorded. These are the first published records of predation, predation attempts, and anti-predator behaviour involving red-nosed cuxiu.

Dropping to escape: a review of an under-appreciated antipredator defence.

Abstract: Dropping is a common antipredator defence that enables rapid escape from a perceived threat. However, despite its immediate effectiveness in predator-prey encounters (and against other dangers such as a parasitoid or an aggressive conspecific), it remains an under-appreciated defence strategy in the scientific literature. Dropping has been recorded in a wide range of taxa, from primates to lizards, but has been studied most commonly in insects. Insects have been found to utilise dropping in response to both biotic and abiotic stimuli, sometimes dependent on mechanical or chemical cues. Whatever the trigger for dropping, the decision to drop by prey will present a range of inter-related costs and benefits to the individual and so there will be subtle complexities in the trade-offs surrounding this defensive behaviour. In predatory encounters, dropping by prey will also impose varying costs and benefits on the predator - or predators - involved in the system. There may be important trade-offs involved in the decision made by predators regarding whether to pursue prey or not, but the predator perspective on dropping has been less explored at present. Beyond its function as an escape tactic, dropping has also been suggested to be an important precursor to flight in insects and further study could greatly improve understanding of its evolutionary importance. Dropping in insects could also prove of significant practical importance if an improved understanding can be applied to integrated pest-management strategies. Currently the non-consumptive effects of predators on their prey are under-appreciated in biological control and it may be that the dropping behaviour of many pest species could be exploited via management practices to improve crop protection. Overall, this review aims to provide a comprehensive synthesis of the current literature on dropping and to raise awareness of this fascinating and widespread behaviour. It also seeks to offer some novel hypotheses and highlight key avenues for future research.

Terrestrial behavior in titi monkeys (Callicebus, Cheracebus, and Plecturocebus) : potential correlates, patterns, and differences between genera

Abstract: For arboreal primates, ground use may increase dispersal opportunities, tolerance to habitat change, access to ground-based resources, and resilience to human disturbances, and so has conservation implications. We collated published and unpublished data from 86 studies across 65 localities to assess titi monkey (Callicebinae) terrestriality. We examined whether the frequency of terrestrial activity correlated with study duration (a proxy for sampling effort), rainfall level (a proxy for food availability seasonality), and forest height (a proxy for vertical niche dimension). Terrestrial activity was recorded frequently for Callicebus and Plecturocebus spp., but rarely for Cheracebus spp. Terrestrial resting, anti-predator behavior, geophagy, and playing frequencies in Callicebus and Plecturocebus spp., but feeding and moving differed. Callicebus spp. often ate or searched for new leaves terrestrially. Plecturocebus spp. descended primarily to ingest terrestrial invertebrates and soil. Study duration correlated positively and rainfall level negatively with terrestrial activity. Though differences in sampling effort and methods limited comparisons and interpretation, overall, titi monkeys commonly engaged in a variety of terrestrial activities. Terrestrial behavior in Callicebus and Plecturocebus capacities may bolster resistance to habitat fragmentation. However, it is uncertain if the low frequency of terrestriality recorded for Cheracebus spp. is a genus-specific trait associated with a more basal phylogenetic position, or because studies of this genus occurred in pristine habitats. Observations of terrestrial behavior increased with increasing sampling effort and decreasing food availability. Overall, we found a high frequency of terrestrial behavior in titi monkeys, unlike that observed in other pitheciids.

Prey Composition of Harpy Eagles (Harpia harpyja) in Raleighvallen, Suriname

Abstract: Apex predators are in widespread decline, in many occasions as a consequence of the demise of their prey. Harpy Eagles (Harpia harpyja) are the largest extant eagles on Earth and keystone predators...

Landowner perceptions of livestock predation: implications for persecution of an Amazonian apex predator

Abstract: Apex predators are widely threatened globally and generally considered a priority on the conservation biology agenda. The harpy eagle, Harpia harpyja, is an apex predator threatened by habitat loss and persecution and a flagship species for Neotropical conservation. We investigated the roles of social, economic and environmental factors related to livestock depredation by harpy eagles, causes of reported harpy eagle persecution by local landholders and the intent of future harpy eagle killings. We explored these issues using structured interviews with 184 local livestock owners, who had admitted killing a combined total of 181 harpy eagles. We found that livestock abundance and livestock husbandry were the best positive predictors of levels of self-reported livestock predation by harpy eagles. Domestic livestock reported to be killed by harpy eagles (192) were mainly chickens (47.9%), followed by goats (22.4%), pigs (18.2%) and sheep (8.3%), with pets representing only ~3% of kills. Few harpy eagle killings were related to livestock predation, which accounted for less than 20% of all eagles killed. Instead, the main reason for killing harpy eagles was simple curiosity, and many interviewees reported later regretting their acts. Regarding intent to kill harpy eagles in the future, interviewees’ perceptions of the threat posed to livestock and humans by eagles, and the subjective norm, were unrelated to intent to kill harpy eagles further. The single most important factor in predicting intent to kill harpy eagles was whether the interviewee had suffered livestock predation by eagles in the past. Additionally, the intention to kill eagles was negatively associated with landholding size. Most of our interviewees were relatively large landowners, but they are typically outnumbered by smallholders who are more likely to persecute harpy eagles. Consequently, education, compensation and tourism activities should be directed to smallholders to mitigate unnecessary persecution and mortality of harpy eagles.