Intraspecific Competition, Habitat Quality, Niche Partitioning, and Causes of Intrasexual Territoriality for a Reintroduced Carnivoran

Animals exploring a new environment develop cognitive maps using diverse sensory input and, thereby, gain information needed to establish home ranges. Experiencing, and learning information about, resources should be advantageous to the resident of a home range while lack of such information should put invaders into the home range at a disadvantage. Conspecifics, especially, should avoid the home ranges of one another to ensure that they do not experience reduced resource availability caused by resource depression or depletion. Yet, encountering conspecific competitors of different sexes may elicit responses that can lead to spacing on a landscape that has different costs and benefits on males and females. We tested the hypothesis that female fishers (Pekania pennanti) avoid competition from both males and female conspecifics whereas male fishers avoid competition only from other males. We reintroduced fishers onto our study site in the presence or absence of competitors’ home ranges during late 2009 through 2011. Using satellite transmitters (Argos) and land-based (VHF) telemetry, we monitored fishers and estimated their locations, movements and use of the surrounding landscape during their first 500 days after release. All fishers settled in relatively high-quality habitat but females that encountered the home ranges of conspecifics moved farther, explored larger areas, and settled farther from their release locations than did females that did not encounter a conspecific’s home range. Male fishers exhibited diverse responses upon encountering the home ranges of conspecifics. Thus, female fishers avoid conspecific competition from all fishers, but males tolerate, or impose, competition with females, apparently to increase mating opportunities. These observations are consistent with the movements and strategies of other solitary carnivores.

Sustainable Indigenous Fishing in the Pre-Contact Caribbean: Evidence and Critical Considerations from Carriacou, Grenada

Multiple studies reveal pre-1492 anthropogenic impacts on Caribbean fisheries that are consistent with overfishing, including changes in targeted prey, shifts in marine habitats exploited, and decreases in the average body size of taxa. At the Indigenous Caribbean village of Sabazan (AD 400–1400) on Carriacou, Lesser Antilles, post-AD 800 declines in fishing, increased mollusk collection, and changes in resource patch emphasis accord with the archaeological correlates of resource depression predicted by foraging theory models from behavioral ecology. Here, I apply foraging theory logic and abundance indices incorporating body size and fish habitat to test the predictions of expanded diet breadth, declining prey body size, and shifts to more distant fishing patches that are typically associated with overfishing. Results uphold a significant decrease in overall fishing, which may be due to habitat change associated with the Medieval Warm Period. Indices of fish size and resource patch use do not meet foraging theory expectations for resource depression, however. Instead, they suggest an absence of resource depression in the Sabazan fishery and at least 600 years of sustainable fishing. I review similar findings for other Caribbean archaeological sites with either negative evidence for fisheries’ declines or quantitatively demonstrated sustainable fishing. These sites collectively serve as a critical reminder of the heterogeneous trajectories of Indigenous social–ecological systems in the pre-contact Caribbean and the need for meta-level analyses of the region’s ancient fisheries. I discuss the application of the sustainability concept in archaeological studies of fishing and conclude that a more critical, explicit approach to defining and measuring sustainability in ancient fisheries is needed.

Bootstrapped Motion of an Agent on an Adaptive Resource Landscape

We theoretically show that isolated agents that locally and symmetrically consume resources and sense positive resource gradients can generate constant motion via bootstrapped resource gradients in the absence of any externally imposed gradients, and we show a realization of this motion using robots. This self-generated agent motion can be coupled with neighboring agents to act as a spontaneously broken symmetry seed for emergent collective dynamics. We also show that in a sufficiently weak externally imposed gradient, it is possible for an agent to move against an external resource gradient due to the local resource depression on the landscape created by an agent. This counter-intuitive boot-strapped motion against an external gradient is demonstrated with a simple robot system on an light-emitting diode (LED) light-board.

Isotopic Evidence for Garden Hunting and Resource Depression in the Late Woodland of Northeastern North America

Resource depression and garden hunting are major topics of archaeological interest, with important implications for understanding cultural and environmental change. Garden hunting is difficult to study using traditional zooarchaeological approaches, but isotopic analyses of animals may provide a marker for where and when people exploited nondomesticated animals that fed on agricultural resources. To realize the full potential of isotopic approaches for reconstructing garden hunting practices—and the impacts of agriculture on past nondomesticated animal populations more broadly—a wider range of species, encompassing many “ecological perspectives,” is needed. We use bone-collagen isotopic compositions of animals (n = 643, 23 taxa, 39 sites) associated with the Late Woodland (~AD 900−1650) in what is now southern Ontario to test hypotheses about the extent to which animals used maize, an isotopically distinctive plant central to subsistence practices of Iroquoian-speaking peoples across the region. Results show that although some taxa—particularly those that may have been hard to control—had substantial access to maize, most did not, regardless of the animal resource requirements of local populations. Our findings suggest that this isotopic approach to detecting garden hunting will be more successful when applied to smaller-scale societies.

Beyond Depression? A Review of the Optimal Foraging Theory Literature in Zooarchaeology and Archaeobotany

The use of optimal foraging theory in archaeology has been criticized for focusing heavily on “negative” human-environmental interactions, particularly anthropogenic resource depression, in which prey populations are reduced by foragers’ own foraging activities. In addition, some researchers have suggested the focus on resource depression is more common in the zooarchaeological literature than in the archaeobotanical literature, indicating fundamental differences in the ways zooarchaeologists and archaeobotanists approach the archaeological record. In this paper, we assess these critiques through a review of the literature between 1997 and 2017. We find that studies identifying resource depression occur at similar rates in the archaeobotanical and zooarchaeological literature. In addition, while earlier archaeological applications of optimal foraging theory did focus heavily on the identification of resource depression, the literature published between 2013 and 2017 shows a wider variety of approaches.

Collapse of the world’s largest herbivores

Large wild herbivores are crucial to ecosystems and human societies. We highlight the 74 largest terrestrial herbivore species on Earth (body mass ≥100 kg), the threats they face, their important and often overlooked ecosystem effects, and the conservation efforts needed to save them and their predators from extinction. Large herbivores are generally facing dramatic population declines and range contractions, such that ~60% are threatened with extinction. Nearly all threatened species are in developing countries, where major threats include hunting, land-use change, and resource depression by livestock. Loss of large herbivores can have cascading effects on other species including large carnivores, scavengers, mesoherbivores, small mammals, and ecological processes involving vegetation, hydrology, nutrient cycling, and fire regimes. The rate of large herbivore decline suggests that ever-larger swaths of the world will soon lack many of the vital ecological services these animals provide, resulting in enormous ecological and social costs.