05/09/2024 | Press release | Distributed by Public on 05/09/2024 14:35
Title image: A parrotfish hiding in a coral reef. (Credit: Dmitri Portnov)
Neighbors can be annoying. They may be loud or intrude on your space. But is it worth fighting with them? Parrotfish choose not to.
Top: A male spotlight parrotfish. Bottom: A female spotlight parrotfish. (Credit: Joshua Manning/CU Boulder)
In a new study published August 28 in the journal Ecology, a CU Boulder researcher and his collaborator revealed that the spotlight parrotfish, a brightly colored species found in the shallow waters off Florida and in the Caribbean Sea, behave more tolerantly toward neighboring parrotfish but aggressively toward strangers.
The researchers spent days underwater observing the colorful fish, providing key insight into a species that plays a critical role in both maintaining healthy coral reefs and contributing to the white sand beaches of the Caribbean.
"Parrotfish are an important part of the coral reef ecosystem and the ecological functions it provides," said Joshua Manning, the paper's first author and a post-doctoral researcher in the Department of Ecology and Evolutionary Biology. "Understanding their behavior will help us evaluate whether and how they can buffer the effects of climate change on coral reefs."
Dear enemy
The spotlight parrotfish is one of the largest parrotfish species in the Caribbean reefs, measuring about 1.5 feet long. They have strong, beak-like teeth that allow them to spend up to 90% of the day munching on microscopic organisms that grow on and within the calcium carbonate structures created by corals. As the fish remove coral skeletons, they create space for new corals to grow and produce white sand as their digestive waste.
Joshua Manning
A male parrotfish chases another parrotfish. (Credit: Joshua Manning/CU Boulder)
Scientists have observed this "dear enemy" effect-when territory holders exhibit less aggression toward neighbors than strangers-in squirrels, sparrows, frogs and other animals. Manning and his collaborator, Sophie McCoy, a marine biologist at the University of North Carolina, Chapel Hill, described the phenomenon for the first time in parrotfish.
Manning said that parrotfish might be more aggressive toward floaters because they are more likely to try to oust territory holders and take over their territories. While territory-holding males have better mating opportunities, their constant patrolling and defense efforts take a toll on their body condition. As a result, they must focus their energy on fighting off the most significant threats.
To the team's surprise, floaters seemed to recognize territorial boundaries. Manning noticed that floaters often swam across the reefs using the buffer zones between established territories to avoid aggression.
"These fish may be smarter than what we give them credit for. They seem to recognize neighbors, find the boundaries of territories, and have the capacity to learn and use information," Manning said.
Coral heath
Due to climate change, coral reefs are declining rapidly. Between 2023 and mid-May 2024, scientists have confirmed mass coral bleaching in at least 62 countries and territories worldwide. Coral bleaching happens when corals expel the algae living in their tissues under stressful conditions, such as high ocean temperatures, causing them to turn completely white.
Parrotfish depend on coral reefs for food and shelter. Losses in corals-due to ocean acidification and warming-can have significant impacts on their habitat and populations. At the same time, parrotfish can accelerate reef recovery from bleaching events by creating bare space for new coral larvae to settle and grow.
"Reefs are a vital source of food for us and support immense biodiversity, including species with significant medical potential. By studying how parrotfishes use space and how their grazing influences coral recruitment patterns, we can better understand how reefs can recover from disturbances and adapt to climate change," Manning said.
At the start of the video, a male stoplight parrotfish foraging in the reef. At 20 seconds, a male stoplight parrotfish aggressively chasing another male along the reef. At 34 seconds, two neighboring males engaging in a much less aggressive interaction, displaying their fins at one another. (Credit: Joshua Manning/CU Boulder)