Newsroom: How to measure chicken behavior accurately

Have you ever wondered how scientists determine what behaviors animals have ? It’s not as simple as just looking at them —especially when researchers are working with large groups of animals, like chickens. So, how do scientists accurately capture the behaviors they’re interested in ?

The ideal method for measuring animal behavior accurately is a method called continuous observation. In this approach, researchers monitor every moment, noting the exact start and end time of each behavior, ideally without missing anything. Unfortunately, this method is incredibly time-consuming and labor-intensive, especially when dealing with live observations or with large animal groups [1].

That’s why many researchers use a more efficient alternative: instantaneous scan sampling. Instead of continuously observing the animals every second, scientists record their behavior at set intervals, like taking a quick snapshot of their behavior every few minutes. For example, they might record a chicken’s behavior every 10 minutes. This method saves time, but it raises an important question: How do researchers know if the interval they choose is the right one? If the interval is too long, they could miss the behaviors. For instance, imagine a researcher is sampling the foraging (feeding) behavior of a hen every 30 minutes over the course of 10 hours. If the data shows the hen is foraging only 1 out of 20 times, should the researcher conclude that the hen doesn’t forage much? Or is it possible that the foraging behavior is happening too quickly to be accurately captured by the 30-minute interval?

While there is existing research on how to validate behavioral sampling methods in chickens [2], the choice of sampling intervals in poultry (chicken) studies can still feel arbitrary. Studies may work with birds of different strains, at different ages or under different environments which can impact the behavioral time budgets [3]. These are what led researchers at UC Davis to take a closer look at this topic. They decided to investigate effective sampling intervals to estimate how young laying hens use structures in an aviary system (depicted in the photo to the right), which is an 3D structure that provides the birds with aerial access. In this study, young hens, also called pullets before reaching maturity at 18 weeks of age, were raised in pens with an aviary structure that included an elevated platform, three perches, and a ramp to help them move to higher areas especially when they were little. To address the limited information on pullets in the current literature, the researchers measured how often the pullets used each resource by observing 20 pullets continuously over six hours, at 6 and 12 weeks of age.

From the continuous data, they tested five different intervals: 1, 5, 10, 15, and 30 minutes. They compared the frequency the birds use the resource under each interval with the actual frequency of resource usage. Only intervals that met three mathematical criteria were considered reliable for capturing how frequently the pullets used each resource.

Here’s what they found:
● For perch use at 6 weeks of age, intervals up to 5 minutes accurately captured the frequency of use when compared to the continuous observation. At 12 weeks, intervals up to 15 minutes were reliable.
● For ramp and platform use, intervals up to 15 minutes were accurate for both 6 and 12 weeks of age.
● For ground use, all intervals accurately captured usage at 6 weeks, but at 12 weeks, intervals up to 10 minutes were necessary for accuracy.
These results show that different behaviors and ages require varying sampling intervals. More importantly, the study highlights the need to validate sampling methods for each behavior and age group independently, rather than relying on one-size-fits-all intervals.

1. Bateson, M., & Martin, P. (2021). Measuring Behaviour: An Introductory Guide (4th ed.). Cambridge: Cambridge University Press. doi:10.1017/9781108776462
2. Daigle, C. L., & Siegford, J. M. (2014). When continuous observations just won’t do: Developing accurate and efficient sampling strategies for the laying hen. Behavioural Processes, 103, 58–66. https://doi.org/10.1016/j.beproc.2013.11.002
3. Makagon, M., Blatchford, R. (2017). Understanding poultry behavior, Applegate, T. (Eds.), Achieving sustainable production of poultry meat, Volume 3: Health and welfare, Burleigh Dodds Science Publishing, Cambridge, UK

Cloude Shao is a 2nd year PhD student in the Animal Behavior Graduate Group.

[Edited by Isabelle McDonald-Gilmartin and Nicole Rodrigues]