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Biology subjects

Grady, J. M.

Publications and source records attributed to Grady, J. M..

3 recordsLinked to original sources

Mice use predictive environmental cues to adapt predatory behavior in hunting tasks of variable difficulty

Prey capture has long served as a model of complex, multimodal behavior with ethological relevance. In this context, the ability of laboratory animals to capture fleeing prey has been investigated in terms of the sensory systems and neuroanatomical regions required for successful capture. While the ability to hunt is experience-dependent, prey capture is often assumed to be a reflexive behavior, governed by innate neural circuits and a basic drive to obtain food. Whether hunting performance depends on complex learning and cognitive strategy remains largely untested, in part because it is difficult to systematically manipulate the difficulty of predator-prey interactions. To address this, we varied ambient temperature across thousands of trials in which laboratory mice pursued cold-blooded cockroaches, whose movement speed was directly determined by body temperature. As expected, capture difficulty increased as a function of temperature. To test whether mice rely on external cues to adjust their predatory behavior, we then mismatched the ambient temperature and that of the prey, finding that mice learn to use relevant environmental information to inform their hunting strategy. Our results suggest that animals can extract and apply meaningful information from predictive environmental cues to adapt their learned behavior.

animal behavior and cognition↗

Temperature-dependent predation predicts a more reptilian future

Vertebrate diversity increases toward the tropics, but the extent to which this pattern varies with thermoregulatory strategy is unknown. A strong divergence, if confirmed, would imply a global restructuring of vertebrate communities with temperature. Here we present evidence for a novel latitudinal and thermal gradient of comparative vertebrate diversity. Synthesizing over 34,000 terrestrial species distributions, we observe a two-orders-of-magnitude shift in comparative richness with temperature, from endothermic dominance in temperate habitats and high elevations, toward parity with ectotherms in the lowland tropics. Next, we provide experimental support for an underlying thermal gradient of predation. Using machine vision tracking in over 4,500 endotherm-ectotherm predation trials, we show that thermally-mediated differences in performance favor endotherm predators in colder conditions and yield theoretically predicted outcomes, including strike count, distance traveled, and time to capture ectotherm prey. Finally, we integrate theory and data to forecast future patterns of diversity, revealing that as the world gets warmer, it will become increasingly reptilian.

ecology↗

Life history scaling and the division of energy in forests

The competition for light has long been regarded as a key axis of niche partitioning that promotes forest diversity, but available evidence is contradictory. Despite strong tradeoffs between growth and survival with light, field tests suggest neutral forces govern tree composition across forest gaps and resource use across size classes. Here we integrate scaling and niche theory, and use data from >114,000 woody plants in a tropical, old growth forest to test and predict patterns of niche partitioning with size and light. Consistent with predictions, the relative abundance, production, light capture, and richness of species in life histories with fast growth follow a power law relationship, increasing 1-2 orders of magnitude along a solar and size gradient. Competitive neutrality between size classes emerges above the sapling layer, where increasing access to light is counterbalanced by stronger self-shading. Convergent power law patterns of resource partitioning across taxa and spatial scale suggest general life history tradeoffs drive the organization of diverse communities.

ecology↗