Large-scale population disappearances and cycling in the white-lipped peccary, a tropical forest mammal

Many vertebrate species undergo population fluctuations that may be random or regularly cyclic in nature. Vertebrate population cycles in northern latitudes are driven by both endogenous and exogenous factors. Suggested causes of mysterious disappearances documented for populations of the Neotropical, herd-forming, white-lipped peccary (Tayassu pecari, henceforth “WLP”) include large-scale movements, overhunting, extreme floods, or disease outbreaks. By analyzing 43 disappearance events across the Neotropics and 88 years of commercial and subsistence harvest data for the Amazon, we show that WLP disappearances are widespread and occur regularly and at large spatiotemporal scales throughout the species’ range. We present evidence that the disappearances represent 7–12-year troughs in 20–30-year WLP population cycles occurring synchronously at regional and perhaps continent-wide spatial scales as large as 10,000–5 million km². This may represent the first documented case of natural population cyclicity in a Neotropical mammal. Because WLP populations often increase dramatically prior to a disappearance, we posit that their population cycles result from over-compensatory, density-dependent mortality. Our data also suggest that the increase phase of a WLP cycle is partly dependent on recolonization from proximal, unfragmented and undisturbed forests. This highlights the importance of very large, continuous natural areas that enable source-sink population dynamics and ensure re-colonization and local population persistence in time and space.

Interference competition between Pecari tajacu and Odocoileus virginianus

Sympatric species, having similar requirements, tend to compete for resources, especially in places where these are limited. Through monitoring with camera traps in waterholes in the Calakmul Region, two competition events were recorded due to interference between the collared peccary (Pecari tajacu) and the white-tailed deer (Odocoileus virginianus), confirming this antagonistic behavior as a strategy to access a shared and limited resource in this zone.  

Occupancy rate and observations of Baird’s tapir (Tapirella bairdii) near waterholes in the Maya forest corridor, Belize

It is estimated that 25 % of the mammal species in the world are at risk of extinction due to habitat loss, fragmentation, farming, and overexploitation. Baird’s tapir (Tapirella bairdii), an ungulate with part of its distribution within the Maya Forest, is at risk of extinction. Waterholes, a primary source for water and an essential element for the survival of tapirs, were the target of this study design. We used a camera-trap survey to determine tapir occupancy and detection rate probability models at seven survey stations at Runaway Creek Nature Reserve which is located within the Maya Forest Corridor in central Belize. The survey was carried out from March to September 2015 and from January 2017 to October 2019 with a total sampling effort of 8,932 camera-trap nights. Our results indicated a cumulative naïve occupancy estimate of 85.7 %, a rate probability of occupancy of 0.97 +/- 0.15 (SE), and a probability of detection of 0.14 +/- 0.01 for all sites and years. The results of occupancy models with human infrastructure covariate showed that the distance to roads model had the highest influence on tapir occurrence (β = -0.95 +/- 0.87), followed by the village covariate model (β = 0.77 +/- 0.99). The topographic covariate of river model (β = 0.47 +/- 0.85) had minimal support. This study highlights the critical importance of waterholes for survival of tapirs, and the influence of roads on tapir occurrence at Runaway Creek Nature Reserve.

Emergent group level navigation: an agent-based evaluation of movement patterns in a folivorous primate

The foraging activity of many organisms reveal strategic movement patterns, showing efficient use of spatially distributed resources. The underlying mechanisms behind these movement patterns, such as the use of spatial memory, are topics of considerable debate. To augment existing evidence of spatial memory use in primates, we generated movement patterns from simulated primate agents with simple sensory and behavioral capabilities. We developed agents representing various hypotheses of memory use, and compared the movement patterns of simulated groups to those of an observed group of red colobus monkeys (Procolobus rufomitratus), testing for: the effects of memory type (Euclidian or landmark based), amount of memory retention, and the effects of social rules in making foraging choices at the scale of the group (independent or leader led). Our results indicate that red colobus movement patterns fit best with simulated groups that have landmark based memory and a follow the leader foraging strategy. Comparisons between simulated agents revealed that social rules had the greatest impact on a group's step length, whereas the type of memory had the highest impact on a group's path tortuosity and cohesion. Using simulation studies as experimental trials to test theories of spatial memory use allows the development of insight into the behavioral mechanisms behind animal movement, developing case-specific results, as well as general results informing how changes to perception and behavior influence movement patterns.