Analysis of ants’ rescue behavior reveals heritable specialization for first responders

Abstract

In colonies of Cataglyphis cursor ants, a single queen mates with multiple males, creating the foundation for heritable behavioral specializations. A novel and unique candidate for such specializations is rescue behavior, a precisely delivered form of altruism in which workers attempt to release trapped nestmates and which relies on short-term memory of previous actions to increase its efficiency. Consistent with task specialization, not all individuals participate; instead, some individuals move away from the victim, which gives rescuers unrestricted access. Using a bioassay to identify rescuers and non-rescuers, coupled with paternity assignment via polymorphic microsatellite markers, we not only show that rescue behavior is heritable, with 34% of the variation explained by paternity, but also establish that rescue, heretofore overlooked in analyses of division of labor, is a true specialization, an ant version of first responders. Moreover, this specialization emerges as early as 5 days of age, and the frequency of rescuers remains constant across ants’ age ranges. The extremely broad range of these ants’ heritable polyethism provides further support for the critical role of polyandry in increasing the efficiency of colony structure and, in turn, reproductive success.

Rescue specialists in Cataglyphis piliscapa ants: The nature and development of ant first responders

“…This difference between individuals in the performance of rescue behavior suggests that some ants are specialized to perform it. Previous research in our laboratories showed that rescue behavior in C. piliscapa is inherited patrilineally from one of several males that fertilize the single colony queen's eggs (Andras et al, 2020) and, thus, is like other heritable specializations in this species (Eyer et al, 2012). Nonetheless, additional behavioral analysis is needed to confirm that rescue is, indeed, such a specialization in C. piliscapa's division of labor.…”

“…Importantly, in asking these questions, we do not presuppose any particular mechanism of recognition, nor do we assume that the mechanism is necessarily complex. Because rescuers and nonrescuers differ genetically (Andras et al, 2020), any preferential treatment, whether of all other rescuers generally or only of rescuers from the same patriline, could be mediated by some form of simple markers produced by these genetic differences. For example, such differences could result in different chemical signatures, a well-known means of communication, as well as nestmate recognition and discrimination, in ants (for reviews, see d 'Ettorre et al, 2017;Schultner & Pulliainen, 2020).…”

“O Sister, Where Art Thou?”—A Review on Rescue of Imperiled Individuals in Ants

“…One of the most recent studies on the topic of rescue behavior in ants addressed the issue of the heritability of rescue activity [ 54 ]. The authors noted that in C. cursor ants, not all individuals engage in rescue actions towards their nestmates, so some of them are possibly genetically specialized for rescue behavior.…”

“…The laboratory simulation of entrapment, although initially treated as a simulation of an ant becoming entrapped by collapsing sand or debris [ 32 ], at some point came to be viewed as a simulation of an ant falling inside an antlion trap and thus facing a predatory threat as well (e.g., [ 42 , 54 ]). In other words, rescue behavior, particularly in sand-dwelling ants, started to be viewed as evidence of an anti-predatory strategy of the ants, which led to claims of coevolution between ants and antlions [ 19 , 20 ].…”

“…The most recent relevant work considered the fact that the laboratory simulation of entrapment is a versatile test, which can be adapted for different experimental setups [ 57 ]. For example, the response to an artificially ensnared victim might be measured in the field, close to the nest entrance (e.g., [ 34 ]); in the laboratory, with a group of potential rescuers (e.g., [ 40 ]) or with a single potential rescuer (e.g., [ 50 ]); in an unmarked area, with a pheromone-free substrate (e.g., [ 43 ]); or in a marked area known to the tested ants (e.g., [ 54 ]). In addition, it was already indicated by earlier works that the test context might be an important factor in terms of rescue behavior expression [ 43 , 48 ].…”