24-year study shows how climate change is reshaping relationships between owls and their prey in Chile

A study conducted in Fray Jorge National Park in northern Chile reveals that changes in rainfall and temperature affect not only food availability for many species, but also the way predators and prey interact. The findings, published in the journal Ecography, show that these relationships change over time and offer new insights into how semi-arid ecosystems respond to climate change.

What happens when rainfall becomes scarce and resources decline? This was the question that led a team of researchers to analyze the diets of three owl species—the barn owl, burrowing owl and great horned owl—over a 24-year period. All three species inhabit this ecosystem in Chile’s Coquimbo Region, one of the country’s main sites for long-term ecological research and part of the LTSER Chile Network.

The answer was recorded in a unique biological archive: 16,932 owl pellets, or masses of undigested remains that owls regurgitate after feeding. These pellets contain bones, fur, feathers and other remains of their prey. Through this long-term monitoring, the researchers reconstructed how predator-prey relationships changed between 1990 and 2015, revealing that climate variability not only alters food availability, but also the structure of food webs.

“Pellets collected during each sampling period represent a snapshot of what is happening at a given moment. When they are collected over many years—as they were in this case, for more than two decades—they become a true ecological archive. A predator’s diet reflects which resources were available at that time and therefore provides indirect information about the state of the ecosystem. That is why the phrase Tell me what you have eaten over the years, and I will tell you about your environment makes so much sense in this study,” says Jazmin Quiroz, a PhD candidate at the University of La Serena (ULS), a student at the Institute of Ecology and Biodiversity (IEB), and lead author of the study.

The research was also led by Angéline Bertin (ULS and IEB) and included Alejandra Troncoso (ULS and IEB), Adriana Lozada (University of La Serena), Nicolás Gouin (ULS and IEB), and Douglas A. Kelt (University of California), among other researchers from Chile and abroad.

The research team also recognizes scientists Peter Meserve (University of Idaho, Moscow) and Julio Gutiérrez (IEB), who passed away in 2026 and 2024, respectively, leaving an important legacy in the scientific community and in long-term research in this ecosystem.

Key findings

To understand how interactions between owls and their prey change, and what role climate and food availability play in these changes, the study focused on three of the five owl species recorded in this Biosphere Reserve: the barn owl (Tyto furcata), which feeds mainly on small mammals; the burrowing owl (Athene cunicularia), a generalist predator that consumes both arthropods and small vertebrates; and the great horned owl (Bubo virginianus), a larger predator with a broad diet dominated by mammals, along with a variety of invertebrates.

The researchers found that during periods of low rainfall, when food resources became less available, the different owl species tended to specialize on different prey, thereby reducing competition among them.

However, beginning in 2003, they detected a broader-scale change. In addition to maintaining this dietary specialization, the owls began incorporating new prey species into their diets, increasing the diversity of the food web. Temperature emerged as the main factor associated with these long-term changes.

“We observed that relationships between owls and their prey respond to climate variability at different time scales. As food availability changes, species adjust their diets. This means that during some periods they share more prey, while during others they specialize on different resources,” says Alejandra Troncoso, co-author of the study.

According to Angéline Bertin, the findings suggest that changing environmental conditions are reshaping predator-prey interactions. “As climate change intensifies, the fragility of these ecological networks may become increasingly evident. Understanding how climate and resource availability shape these dynamics will be essential for predicting ecosystem resilience,” she explains.

An ecosystem shaped by climate

Fray Jorge National Park provides a natural laboratory for studying these processes. Its location in the semi-arid region of northern Chile means that rainfall varies considerably from year to year due to phenomena such as El Niño and La Niña. In recent decades, the ecosystem has also experienced a sustained decline in precipitation associated with the megadrought affecting central Chile.

For the researchers, the study’s main contribution lies not only in demonstrating that owls alter their diets, but also in showing that climate can reorganize relationships among species across an entire ecosystem.

“The owls are showing us how species adjust to an ecosystem where resources are highly variable. At the same time, these results show that even a highly protected system such as Fray Jorge National Park depends on resource availability to maintain the functioning of its ecological networks. This invites us to ask what happens in landscapes with greater human intervention and less vegetation cover,” says Alejandra Troncoso.

Jazmin Quiroz emphasizes that changes in climate do affect food availability for predators. “If the megadrought persists or intensifies, these changes are also expected to become more pronounced, potentially generating ecological networks that are more fragile and less resilient to new disturbances,” she says.

Beyond its findings, the study highlights the importance of maintaining long-term ecological research to understand the effects of climate change and other human pressures, and to anticipate how ecosystems will respond in the coming decades. The study also recognizes the legacy of ecologists such as Peter Meserve and Julio Gutiérrez, who helped establish and advance this type of research within this valuable ecosystem.

Finally, lead author Jazmin Quiroz emphasizes the importance of Fray Jorge National Park as a unique natural laboratory. “As a protected area with long-term ecological monitoring and well-documented biodiversity, it is an ideal place to study interactions among species and generate fundamental knowledge to predict the resilience of other ecosystems as arid zones expand as a result of climate change.”

By Carolina Todorovic

A study conducted in Fray Jorge National Park in northern Chile reveals that changes in rainfall and temperature affect not only food availability for many species, but also the way predators and prey interact. The findings, published in the journal Ecography, show that these relationships change over time and offer new insights into how semi-arid ecosystems respond to climate change.

What happens when rainfall becomes scarce and resources decline? This was the question that led a team of researchers to analyze the diets of three owl species—the barn owl, burrowing owl and great horned owl—over a 24-year period. All three species inhabit this ecosystem in Chile’s Coquimbo Region, one of the country’s main sites for long-term ecological research and part of the LTSER Chile Network.

The answer was recorded in a unique biological archive: 16,932 owl pellets, or masses of undigested remains that owls regurgitate after feeding. These pellets contain bones, fur, feathers and other remains of their prey. Through this long-term monitoring, the researchers reconstructed how predator-prey relationships changed between 1990 and 2015, revealing that climate variability not only alters food availability, but also the structure of food webs.

“Pellets collected during each sampling period represent a snapshot of what is happening at a given moment. When they are collected over many years—as they were in this case, for more than two decades—they become a true ecological archive. A predator’s diet reflects which resources were available at that time and therefore provides indirect information about the state of the ecosystem. That is why the phrase Tell me what you have eaten over the years, and I will tell you about your environment makes so much sense in this study,” says Jazmin Quiroz, a PhD candidate at the University of La Serena (ULS), a student at the Institute of Ecology and Biodiversity (IEB), and lead author of the study.

The research was also led by Angéline Bertin (ULS and IEB) and included Alejandra Troncoso (ULS and IEB), Adriana Lozada (University of La Serena), Nicolás Gouin (ULS and IEB), and Douglas A. Kelt (University of California), among other researchers from Chile and abroad.

The research team also recognizes scientists Peter Meserve (University of Idaho, Moscow) and Julio Gutiérrez (IEB), who passed away in 2026 and 2024, respectively, leaving an important legacy in the scientific community and in long-term research in this ecosystem.

Key findings

To understand how interactions between owls and their prey change, and what role climate and food availability play in these changes, the study focused on three of the five owl species recorded in this Biosphere Reserve: the barn owl (Tyto furcata), which feeds mainly on small mammals; the burrowing owl (Athene cunicularia), a generalist predator that consumes both arthropods and small vertebrates; and the great horned owl (Bubo virginianus), a larger predator with a broad diet dominated by mammals, along with a variety of invertebrates.

The researchers found that during periods of low rainfall, when food resources became less available, the different owl species tended to specialize on different prey, thereby reducing competition among them.

However, beginning in 2003, they detected a broader-scale change. In addition to maintaining this dietary specialization, the owls began incorporating new prey species into their diets, increasing the diversity of the food web. Temperature emerged as the main factor associated with these long-term changes.

“We observed that relationships between owls and their prey respond to climate variability at different time scales. As food availability changes, species adjust their diets. This means that during some periods they share more prey, while during others they specialize on different resources,” says Alejandra Troncoso, co-author of the study.

According to Angéline Bertin, the findings suggest that changing environmental conditions are reshaping predator-prey interactions. “As climate change intensifies, the fragility of these ecological networks may become increasingly evident. Understanding how climate and resource availability shape these dynamics will be essential for predicting ecosystem resilience,” she explains.

An ecosystem shaped by climate

Fray Jorge National Park provides a natural laboratory for studying these processes. Its location in the semi-arid region of northern Chile means that rainfall varies considerably from year to year due to phenomena such as El Niño and La Niña. In recent decades, the ecosystem has also experienced a sustained decline in precipitation associated with the megadrought affecting central Chile.

For the researchers, the study’s main contribution lies not only in demonstrating that owls alter their diets, but also in showing that climate can reorganize relationships among species across an entire ecosystem.

“The owls are showing us how species adjust to an ecosystem where resources are highly variable. At the same time, these results show that even a highly protected system such as Fray Jorge National Park depends on resource availability to maintain the functioning of its ecological networks. This invites us to ask what happens in landscapes with greater human intervention and less vegetation cover,” says Alejandra Troncoso.

Jazmin Quiroz emphasizes that changes in climate do affect food availability for predators. “If the megadrought persists or intensifies, these changes are also expected to become more pronounced, potentially generating ecological networks that are more fragile and less resilient to new disturbances,” she says.

Beyond its findings, the study highlights the importance of maintaining long-term ecological research to understand the effects of climate change and other human pressures, and to anticipate how ecosystems will respond in the coming decades. The study also recognizes the legacy of ecologists such as Peter Meserve and Julio Gutiérrez, who helped establish and advance this type of research within this valuable ecosystem.

Finally, lead author Jazmin Quiroz emphasizes the importance of Fray Jorge National Park as a unique natural laboratory. “As a protected area with long-term ecological monitoring and well-documented biodiversity, it is an ideal place to study interactions among species and generate fundamental knowledge to predict the resilience of other ecosystems as arid zones expand as a result of climate change.”

By Carolina Todorovic