Rescue Me

Rescue Me

Some have argued that there is strong evidence that empathy has deep evolutionary roots with biochemical and neurological underpinnings and that even the most advanced forms of human empathy are built on basic expressions facilitated by core mechanisms. These physiological mechanisms are proposed to have evolved through social interactions such as group living and parental care. However, the measurement of empathy is problematic. Rescue behaviour by rats that seem to understand their cagemate's distress has been described recently as empathetic (Bartal et al. 2011). Now, in this issue (pp. xx–xx), Karen Hollis (Mount Holyoke College) and Elise Nowbahari (Université Paris 13) demonstrate an analogous rescue behaviour by sand-dwelling ants (Fig. 1). However, rather than arguing that these ants are capable of feeling empathy for their nestmates, they suggest that the seemingly complex rescue behaviours can emerge from simple mechanisms.

A previous study by the same authors (Nowbahari et al. 2009) demonstrated that the sand-dwelling Cataglyphis cursor could rescue experimentally trapped nestmates by digging and limb pulling but that they also used two novel behaviours, transporting excavated sand and carefully biting the nylon thread that held the nestmate down. Rescuing was risky behaviour; they might become buried themselves or if the sand is an antlion trap, they might become prey too. Cataglyphis cursor therefore rescued only nestmates and ignored other trapped conspecifics. Now Hollis and Nowbahari have asked how common rescue behaviour is among other sand-dwelling ant species, whether it is only directed towards nestmates and which ecological variables might promote it.

Rescue behaviour was compared across five additional species of sand-dwelling Mediterranean ants: two species, Cataglyphis floricola and Lasius grandis live in areas of loose sand in which there are also many antlions; Messor barbarus and Messor marocanus inhabit more compact soil and form foraging trails and are thus less likely to become trapped in sand or become prey to antlions. The fifth species, Aphaenogaster senilis, has an intermediate ecology. A loop of thread was tied around the waist of an ant and she was secured to filter paper. She was then partially buried near her nest entrance, the nest entrance of a conspecific or the nest entrance of a heterospecific. Rescue and aggressive behaviours were observed.


Figure 1. A Cataglyphis cursor ant rescuing her nestmate. She has transported sufficient sand away from the victim, exposing the nylon thread snare holding her nestmate snug against the white filter paper and is attempting to bite through it. Photo: P. Devienne (adapted from Nowbahari et al. 2009).

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