Goats work for food in a contrafreeloading task

  • Key finding:

    Contrafreeloading (CFL) is the phenomenon when animals work for a resource although an identical resource is available for free. Possible explanations for CFL are that animals seek context for species-specific behaviours or to control their environments. We investigated whether goats show CFL and whether breeding for productivity traits has altered its occurrence. In a manipulation task, we compared two selection lines: 27 Nigerian dwarf goats, not bred for productivity traits, and 30 dairy goats, bred for high milk yield. Over 10 trials, each goat could either feed for free from an open door, or open a sliding door for a feed of similar value. The results were analysed using an Item Response Tree (IRTree) generalized linear mixed model (GLMM). The probability to participate was high in all trials in both selection lines. With increasing trial number, dwarf goats chose the CFL option more often than in the first trial. Dairy goats chose the closed door at a constant rate and in just under half of the trials. Unlike dwarf goats, dairy goats were faster to approach the closed compared to the open door. Overall, it seems that both selection lines were similarly interested in CFL. The foraging behaviour of pushing open a door for food may give them back a sense of control, and they may find it enjoyable.

Links to Open Access Publications or DOI:


Rosenberger, K., Simmler, M., Nawroth, C., Langbein, J., Keil, N.

Goats work for food in a contrafreeloading task. Scientific Reports 10, 22336 (2020).