The ‘Dear Enemy Effect’
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The ‘Dear Enemy Effect’
The relationship between territorial animals is explained chiefly using the ‘dear enemy effect,’ which states that the animals became less aggressive towards their neighbors than strangers. The two hypotheses used to define the ‘dear enemy effect’ phenomena are the familiarity and threat-level hypothesis. The familiarity hypothesis maintains that aggression between neighbors reduces when their relationship settles. The threat-level hypothesis holds that residents are more aggressive to the group posing the more significant threat. Strangers pose the bigger threat since they may be looking for mates and territories, unlike neighbors who only compete for mates. Therefore, both the threat-level and familiarity hypothesis predict residents being more aggressive to strangers than to neighbors.
Most of the ‘dear enemy effect’ studies focus on mammals and birds since there is an expectation that the two groups would exhibit the phenomenon. Most researchers avoid studies that do not show the ‘dear enemy effect’ due to the difficulty of interpreting results. Muller and Manser, in their research “Nasty neighbors rather than dear enemies in carnivore” look at the ‘dear enemy effect’ in the banded mongoose (Mungos mungo), which is a small animal in the carnivore family, a group largely left out in the studies (Müller & Manser, 2007). On the other hand, Tumulty et al. investigates the ‘dear enemy effect of the brilliant-thighed poison frog (Allobates femoralis) (Tumulty et al., 2018)
Banded mongoose in the Muller and Manser study live in stable units usually formed when a splinter group of the same sex joins with a splinter group of the opposite sex. The groups also form when one splinter group of the same sex chases away a splinter group of the same sex in a group and takes over. To understand the relationship of the residents, neighbors, and strangers of the banded mongoose, Muller and Manser investigated the worry calls, the countermarking, and inspection bouts number and duration. The results showed a great contrast to the threat-level and familiarity hypothesis. More adult banded mongooses emitted worry calls, and there were more inspection bouts by individuals responding to scent marks of neighbors than of strangers (Müller & Manser, 2007). The worry calls brought other group members to the sight, while the increase in inspection bouts gathered more information about the neighbors. The worry calls and inspection bouts were less for strangers as the residents were likely not to reencounter the group, posing a lesser threat. There was no difference in countermarking of residents, strangers, and neighbors, indicating that the countermarks were not used for territory defense.
Many frog species have males protecting their territories where females deposit their eggs. Tumulty et al. look at whether the brilliant-thighed poison frogs’ calls differ for neighbors and strangers while defending their territory. The brilliant-thighed poison frog protects long-term habitats, usually producing loud distinctive advertisement calls. The study results showed no difference in the frogs’ response to neighbors and that of strangers (Tumulty et al., 2018). Although the calls were distinctive, the males’ reaction in the experiments was equally strong and weak in encounters with both neighbors and strangers.
The results from both studies show that the dear enemy relationship is not universal to all territorial animals. In the banded mongoose, they responded more aggressively to neighbors than to strangers since, in their case, neighbors posed a more significant threat. In the case of the brilliant-thighed poison frog, the response was the same for both neighbors and strangers. Researchers still need to do more research, especially concerning brilliant-thighed poison frogs.
References
Müller, C. A., & Manser, M. B. (2007). ‘Nasty neighbors’ rather than ‘dear enemies’ in a social carnivore. Proceedings of the Royal Society B: Biological Sciences, 274(1612), 959-965.
Tumulty, J. P., Pašukonis, A., Ringler, M., Forester, J. D., Hödl, W., & Bee, M. A. (2018). Brilliant-thighed poison frogs do not use acoustic identity information to treat territorial neighbors as dear enemies. Animal behavior, 141, 203-220.https://www.researchgate.net/profile/AndriusPasukonis/publication/326044939_Brilliantthighed_poison_frogs_do_not_use_acoustic_identity_information_to_treat_territorial_neighbours_as_dear_enemies/links/5bb18bc945851574f7f39961/Brilliant-thighed-poison-frogs-do-not-use-acoustic-identity-information-to-treat-territorial-neighbours-as-dear-enemies.pdf