Macquarie University, Australia 2022 PhD Scholarships in Evolution of Cognition

Many animals need to return to rewarding locations, be that home, good foraging places, or places to find mates.  Here the project would be to compare how animals with very different brains (bees and hummingbirds) solve a very similar navigational problem: relocating rewarding flowers. These evolutionary distant species all forage for nectar in flowers scattered around their familiar environment. They return to rewarding flowers and appear to use similar kinds of information to do so albeit with very different visual systems and, more importantly, with brains vastly different in structure and neural capacity. Here we would test a specific hypothesis (proposed by Macquarie partner Barron) that although the task is the same, the very different neural capabilities of these animals means that how these animals return to rewarding flowers is very different. Both optimal foraging models and observational data from the 1970’s and 1980’s suggested that nectarivores (including bees and hummingbirds) foraged among flowers with rule-based movements. But with increasing data, it became clear that the behaviour of hummingbirds is complex, flexible, and involved learning and memory. For the past three decades, Healy and her collaborators, in conducting experimental manipulations in the field with free-living hummingbirds, have provided evidence that these birds can learn and remember far more than was considered possible, given their brain size.  To address whether differences in brain structure, connectivity and information flow enable foraging capacities in these birds that are both qualitatively and quantitatively different from the foraging capacities of bees.  The student will employ a deceptively simple strategy of comparing hummingbirds and bees on the same tasks. For all the analyses of the capacities of these two taxa, they have not previously been directly compared.  Importantly, the project will bring together two PIs with considerable experience in testing each of the two taxa.  This is crucial because it would be easy to show differences between the performance of hummingbirds and bees simply by asking both species to solve problems better suited to one than to the other.  For example, Healy’s group has shown that rufous hummingbirds prefer to use spatial rather than colour cues to relocate flowers so tests that use colour as a key cue need to have all spatial cues removed.  This deep knowledge of problem-solving by hummingbirds (matched by Barron’s expertise with bees), combined with a wealth of methods that have exposed novel cognitive capacities of hummingbirds puts this combination of PIs in the ideal position to supervise a PhD student’s examination of the neural capacities in wild, free-moving bees and hummingbirds. The student would specifically seek the limit of the capacity of bees in spatial cognition, using tasks such as traplining (where animals learn a sequence of rewarding locations using an optimal route), or episodic-like memory (memories for what-where-when). By appropriate manipulations, such as inserting a barrier, they will determine whether bees and hummingbirds use a cognitive map or simpler vector-based heuristics (like the nearest neighbour) to move around the flowers. By (for example) increasing the number of flowers along the route or in the patch, we can determine whether there is a switch point between foraging strategies and whether bees switch sooner than do hummingbirds.