Collaborative Research: An interdisciplinary approach to understand selfish parental care of egg and larvae in mixed-species communal nest breeding freshwater fishes

Faced with danger such as a predator, animals commonly exhibit selfish behavior to gain survival advantages over others when in a herd, school, flock, or swarm. What is not widely documented, but probably common, is whether animals selfishly protect their young at the expense of others when they have control over an assemblage consisting of their own young mixed with others unrelated to them.

This study will investigate such possible selfish protection of eggs and larvae orchestrated by fish parents when their eggs are mixed with those of other species in their nest. By characterizing water flow and oxygen levels and risk of predation of eggs in various locations in the nest and genetically identifying the species of eggs found in these locations, the researchers will be able to determine the relative quality and safety of the locations where the nest host places its eggs for incubation and whether that indicates selfish parental care behavior.

They also will observe fish behaviors during nest building and spawning, directly and with videography, to interpret placement and defense of eggs in the context of selfishness, nest parasitism, and the selfish herd theory. As species unique to North America, mound-nest building minnows represent a natural and cultural heritage that scientists have largely overlooked in their studies of animal behavior.

Communicating improved understanding of these fishes to the general public through a documentary grounded in science and artistic performances, will ensure effective publicization of scientific knowledge to garner support for preservation of native freshwater fishes with unique behaviors and ecosystem roles.

Selfishness underpins most animal behaviors as individuals act to maximize their own fitness, often at others’ expense. Using a putatively mutualistic communal nest breeding freshwater fish system, this study will expand Hamilton’s selfish-herd theory in two key ways by: 1) including an abiotic stimulus as a defining threat for individual selfish behavior, and 2) recognizing that embryonic ‘herds’ may be created by parents to confer selfish-herd benefits on their brood in an incubation environment.

Specifically, this study will: i) Investigate how ambient dissolved oxygen modifies the relationship between fitness and spatial position in a mixed-species egg and larval aggregation formed to reduce predation risk, ii) Determine if and how selfish-herd effect is conferred on incubating host brood through egg and larval distribution in a mixed-species freshwater fish nest-association, and iii) Bridge the public-knowledge gap about breeding behaviors (nest building, spawning, agonistic combat, and cooperative-competitive interactions) and ecosystem roles of native freshwater fishes. Built on an interdisciplinary collaboration between biologists, geoscientists and computational engineers, this study will be the first to characterize selfish-herd behavior in a three-dimensional incubation environment, using a combination of field observations, experimentation, and high-precision, physics-based simulation of water and silt movement and dissolved oxygen dynamics in mound nests.

The investigator’s will use a novel application of computational fluid dynamics to characterize aquatic nest abiotic environment and its consequence for survival of eggs and larvae. Success of this study will provoke fundamental rethinking of some “nest-parasitism” phenomena, common among birds and fishes, as potentially context-dependent mutualisms.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.