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.

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

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 We collated published and unpublished data from 86 studies across 65 localities to assess titi monkey (Callicebinae) terrestriality.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.

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

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...

https://journals.sagepub.com/doi/pdf/10.1177/1940082918800789

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

Honest error, precaution or alertness advertisement? Reactions to vertebrate pseudopredators in red‐nosed cuxiús (Chiropotes albinasus), a high‐canopy neotropical primate

Many vertebrate taxa respond to heterospecific alarm calls with anti-predator behaviours. While it is unclear how apparent recognition is achieved, learned associations between the occurrence of the call and the presence of a predator are considered the most likely explanation. Conclusive evidence that this behaviour is indeed underpinned by learning, however, is scarce. This study tested whether wild black capuchin monkeys (Sapajus nigritus) learn to associate novel sounds with predators through a two-phase field experiment. During an initial training phase, three study groups were each presented with a playback of one of the three novel sounds together with a simulated felid predator on four occasions over an 8- to 12-week period. This was followed by a test phase, wherein each of the three sounds was played back to individuals in all three groups, allowing each sound to serve as both a test stimulus for individuals trained with that sound, and a control stimulus for individuals trained with another sound. Antipredator responses were significantly stronger in response to test sounds than to controls. Limited observations suggest that antipredator responses persisted for at least 2 years without reinforcement of the predator–sound link. Additionally, responses to noisier sounds were typically stronger than were those to more tonal sounds, although the effect of sound type cannot be disentangled from potential effects of group. This study provides the strongest evidence to date that learning affects the responses of primates to sounds such as heterospecific alarm calls, and supports the contention that signals provide receivers with information.

/pdf/experimental-evidence-for-heterospecific-alarm-signal-4cckyi9f7s.pdf

Experimental evidence for heterospecific alarm signal recognition via associative learning in wild capuchin monkeys

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.

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

ABSTRACT Neotropical manakins exhibit polygynous lekking systems in which males do not provide paternal care and exhibit elaborate courtship displays. Despite familial patterns, some historical field observations suggested that the Helmeted Manakin (Antilophia galeata) has evolved territoriality rather than lekking and a socially monogamous mating system. Furthermore, the evidence so far does not allow a clear understanding of the role played by resources, such as nesting sites and male behaviour in shaping the mating system in this species. Our objectives were to verify whether territorial behaviour occurs in the Helmeted Manakin and to provide a preliminary assessment of this species’ hypothesised social monogamy. Using an experimental approach with simulated territorial intrusions, we demonstrated that males in this species hold individual territories with nesting sites but do not provide parental care, similar to its congener, the Araripe Manakin (Antilophia bokermanni). Males’ responses occurred more aggressively in central areas of territories. Larger home ranges encompassed the smaller defended territories and the male display consists of repeated circular flights within the territory. Our results indicate that the Helmeted Manakin has a polygamous mating system. However, we suggest the species is better classified within the continuum of a resource-defence exploded-lek mating system. The distinct environmental conditions in which the species evolved may have played a significant role in modifying its behaviour, resulting in patterns that deviate from the typical lekking system found among manakins. This study highlights the importance of investigating atypical manakins to further our understanding of alternative reproductive tactics among birds.

Samara de Albuquerque Teixeira

Papers

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

Honest error, precaution or alertness advertisement? Reactions to vertebrate pseudopredators in red‐nosed cuxiús (Chiropotes albinasus), a high‐canopy neotropical primate

Individual territoriality in lekking species: the case of the Helmeted Manakin