First field evidence for alloparental egg care in cooperatively breeding fish

Abstract

Helping behaviour in cooperative breeders has been intensively studied in many animal taxa, including arthropods, birds and mammals. In these highly social systems, helpers typically engage in brood care and the protection of dependent young. Such helping systems also exist in cooperatively breeding cichlid species of Lake Tanganyika. However, breeding in these species happens in clefts, narrow holes or shelters underneath stones. Therefore, direct brood care by breeders and helpers has thus far only been observed under artificial laboratory conditions. Under natural conditions, brood care behaviour has been estimated indirectly by determining the time spent in the breeding chamber, or by the number of visits to the breeding chamber. The reliability of such substitutes needs to be validated, for instance, by demonstrating alloparental egg care of helpers through direct observations in nature. Here, we describe direct egg care by a male helper of the cooperatively breeding cichlid Neolamprologus savoryi in the field. The helper inspected and cleaned the eggs and defended them against predators. By reconstructing the genetic relatedness using microsatellite markers, we show that the helper was the son of the breeding male, but unrelated to the breeding female. The genetic mother of the helper was defending a different territory next to the one where the helper showed alloparental egg care. This indicates that the helper had dispersed inside the male territory to assist another female to care for his half‐siblings. These results demonstrate alloparental egg care without reproductive share in a fish species under natural conditions, underlining that helping behaviour in cooperatively breeding fish has a strong non‐self‐serving component.

Sex-Specific Routes to Independent Breeding in a Polygynous Cooperative Breeder

“…Even though a large body size yields a reproductive advantage due to enhanced fecundity, investing in early reproduction seems to pay off for females (Josi et al, 2020b). This is partly because N. savoryi females generally lay small clutches (Josi et al, 2019) that are probably not overly constrained by a small body size. Furthermore, like many Lake Tanganyika cichlids, N. savoryi has no distinct breeding season (Heg et al, 2005;Josi et al, 2021) and can produce clutches at a high rate (approx.…”

“…Within years, individuals could be reliably identified using a combination of their size, individual colour patterns and location (Josi et al, 2020b). We re-identified individuals between the 2 years using 14 polymorphic microsatellites (Josi et al, 2019). Additionally, we took genetic samples from individuals in all isolated territories scattered around the focal colony in 2017 in search for potential long-distance dispersers.…”

“…In both years, group compositions were repeatedly checked to identify potential dispersers. Details on microsatellites and genetic analyses are given in Josi et al (2019).…”

“…As in many other polygynous systems males exceed females in size (Heg et al, 2005). Offspring delay dispersal and support the breeder female in egg care, territory maintenance, and defence (Heg et al, 2005;Josi et al, 2019Josi et al, , 2020a. With increasing helper age, relatedness to the dominants decreases due to breeder turn-over, dispersal, and extra-pair parentage (Josi et al, 2021).…”

An Evolutionary Point of View of Animal Ethics

“…More importantly, he tried to find the evolutionary origin of this animal trait, suggesting that it evolved from the selective advantages of kinship behavior in the struggle for life (Darwin, 1872). Such a behavior corresponds, for instance, to alloparental care, which is relatively common in mammals and birds and is now also characterized in fishes and insects (Josi et al, 2019;Wu et al, 2020). After more than one century, the need to define what exactly non-human animals are able to feel and-from this starting point-rethink the legal status and place of animals in human societies is becoming increasingly necessary.…”