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Resource competition explains rare cannibalism in the wild in livebearing fishes

“…In support of our a priori prediction 1a, we found cannibalism was rare in the wild: absent in 14 of the 17 surveyed species, and rare even in the three species (G. manni, G. holbrooki and G. hubbsi) in which we found it. This is in stark contrast to the high cannibalism rates reported from captive settings, experiments and aquaculture (e.g., Baldwin, 1980;Dionne, 1985;Hubbs, 1996;Jones et al, 1998;Naumowicz et al, 2017), but aligns well with previous studies on wild-caught fish, which have often reported cannibalism rates of around 1% (Crivelli & Boy, 1987;Gluckman & Hartney, 2000;Hubbs, 1971Hubbs, , 1991Nesbit & Meffe, 1993;Specziár, 2004). It is also worth noting that several previous gut-content analyses conducted in guppies and Gambusia, did not report any incidence of cannibalism (e.g., Bassar et al, 2010;Crivelli & Boy, 1987;Ganassin et al, 2020;Gkenas et al, 2012;Pirroni et al, 2021;Zandonà et al, 2011Zandonà et al, , 2015.…”

“…One group, the livebearing fishes of the family Poeciliidae, has long been known for the (what appears to be common) occurrence of cannibalism, which has been reported from many different genera (e.g., Belonesox , Gambusia , Heterandria , Poecilia , Poeciliopsis , and Xiphophorus ; Meffe & Snelson, 1989; Manica, 2002; Pereira et al, 2017) and settings (wild populations: e.g., Nesbit & Meffe, 1993; Specziár, 2004; laboratory/experimental settings: e.g., Dionne, 1985; Hubbs & Schlupp, 2008; Meffe, 1984; Nilsson et al, 2011). In fact, this behavior often poses obstacles for breeding poeciliid fishes in aquaculture facilities, laboratory research, and the aquarium hobby (e.g., Baldwin, 1980; Barki et al, 2014; Jones et al, 1998; Naumowicz et al, 2017), and usually takes the form of filial cannibalism (i.e., parents consuming their own offspring) and nonparental cannibalism (i.e., individuals of an older generation cannibalizing unrelated younger conspecifics; Manica, 2002).…”