Larger versus smaller heterospecifics: shoaling behavior in orange chromides, an endemic cichlid of the Indian subcontinent

Abstract

In the biological world, group formation and affiliation to group members is a fascinating area of research as it contributes toward understanding the behavioral strategies of an organism (Parrish and Edelstein-Keshet 1999). Several behavioral studies on animals have been conducted to observe and understand patterns of social group formation, and to investigate the group dynamics under different ecological contexts (Rodgers et al. 2011; Gómez-Laplaza 2012). Among the vertebrate model systems, fish taxa are a popular choice to understand group living behavior (Couzin and Krause 2003). Group living in the form of shoaling and schooling behavior in fishes have been studied in depth (Camacho-Cervantes et al., 2019; Pitcher 1986; Krause et al. 2002; Couzin and Krause 2003; Sumpter et al. 2008; Huntingford and Ruiz-Gomez 2009; Gómez-Laplaza 2012; Meuthen et al. 2016), and it still remains one of the intriguing areas of research in the field of behavioral sciences (Kareklas et al. 2017; Miller 2017; Pouca and Brown 2017). A shoal is defined as an aggregation where the shoaling members maintain a nearest neighbor distance of 3–4 body lengths among each other (Clark and Evans 1954; Pitcher and Parrish 1993). Shoals are more social in nature (Pitcher 1983), and shoaling patterns are influenced by several factors, for example, size of the shoal (Krause et al. 1996), dietary preference (Morrell et al. 2007), phenotypic characteristics (Wong and Rosenthal 2005), developmental stages (Lee-Jenkins and Godin 2010), sex (Ruhl and McRobert 2005), and species identity (Griffiths and Magurran 1997) of the shoaling partners, and availability of resources (Ward et al. 2005), presence or absence of predators (Chivers et al. 1995), and even on physical properties of the aquatic habitat (Ward et al. 2007). Shoaling preferences vary across conditions (McRobert and Bradner 1998; Ward and Hart 2003), and it is generally believed that phenotypically homogenous shoals (Cattelan and Griggio 2020), for example, shoaling with conspecifics, are highly advantageous in terms of diluting predation risk and/or foraging for similar resources (Krause and Godin 1994). However, mixed-species shoaling is also common in fishes. Studies have shown that many fishes choose to shoal with either heteroor conspecifics based on the given