“Character differences between nodes seem to be an important ingredient for the resilience of the whole group,” says Selin Ersoy. “This could make the overall population of knots more resilient to changes in their environment. Knots could copy the foraging behavior of adventurous conspecifics that succeed in new locations.” Ersoy shows for the first time that behavior observed in experimental situations corresponds to real behavioral strategies in nature, on the mudflats of the Wadden Sea. This week, Ersoy earned his PhD for his knot research at the University of Groningen.
Animals have personalities too
Knots of all ages and sexes exhibit behavioral traits. These usually remain unchanged over time, but vary from person to person. Some individuals are more adventurous and exhibit more exploratory behavior in a new environment than others. Other individuals take fewer risks and hardly dare to move in a new environment. These ‘personalities’ have ecological and evolutionary consequences, but to what extent is largely unknown. Few studies have investigated this in the area.
During her PhD research, Selin Ersoy developed a new way to map the variation in personality between individual red knots. She wanted to know if the behavior in experimental situations could be extrapolated to a larger and more complex nature and how individual differences develop. “With our new method, which allowed us to study animal personality, we found that knots likely develop their personality through the experiences they get while growing up,” says Ersoy. “After growing up, adults stick to exploratory behavior. It’s like character types in people.”
Scouts eat higher quality food
Ersoy and her colleagues were even able to predict a number of other behaviors in nature. For example, variation in exploratory personality type (that is, slow versus fast scout) predicts foraging tactics and diet choice in the wild. Fast scouts forage more visually and eat soft prey such as shrimp or worms, while slow scouts mainly forage by feel and feed on hard-shelled prey such as clams. This is a new explanation for variation in foraging specialization between individuals in the same population.
Exploratory behavior is also related to variation in movement across the landscape and over time. Ersoy: “We were surprised to see that slow and fast scouts have distinctly different movement patterns at night, while they move more or less the same way during the day. These different individuals even have different arrival times for migration. Fast scouts arrive later in the Wadden Sea than the slower scouts.” In the future, Ersoy and her colleagues will study where they stay in the meantime. Perhaps these knots take more time to care for their young in the Arctic.
The whole group benefits
“We found striking differences in feeding and movement patterns between slow and fast scout nodes. This suggests that fast scouts can provide information about foraging and new foraging opportunities for entire populations,” says Ersoy. “Such new capabilities are important because knots face pressure from human impacts on their coastal wintering habitat, which is directly related to food availability. Fast scouts can help the entire population cope with environmental change.”
The gap closed between controlled experiments and real Wadden Sea
The goal of determining behavior in experimental settings is to understand the mechanisms behind behavior in nature. Selin Ersoy’s study fills a critical gap between experimental research on wild animals in controlled environments and observed behavior in the wild.
“It is a first step. We should do more similar personality research in other animals and in other natural habitats,” says Ersoy. “We want to know if personalities work in the same way in other species and situations.”
Tracking knot movements with small transmitters
Researchers such as Selin Ersoy track birds using ultra-small radio transmitters placed on their backs during the summer months. Birds don’t mind. These transmitters emit unique signals. These are picked up by antennas spread over the Wadden Sea.
WATLAS is a new system that uses so-called ‘reverse GPS’. The small transmitters, which are temporarily attached to birds, emit a signal themselves. That signal is received by fixed reception stations in and around the Wadden Sea. Due to the minute differences in the time of arrival of the signal between different receivers, the position of the animal-with-transmitter is calculated to within a few meters, from second to second.
Thanks to WATLAS, researchers can watch a migratory bird like the red knot move back and forth very precisely with the ebb and flow in search of food. Because many birds can be equipped with the relatively cheap transmitters at the same time, researchers can now also see the interaction between different animals from their office chairs.
Photos: Selin Ersoy; WATLAS; NIOZ