Effect of egg predator on nest choice and nest construction in sand gobies Topi K. Lehtonen a, b, c, * , Kai Lindström b , Bob B. M. Wong c a Section of Ecology, Department of Biology, University of Turku, Turku, Finland b Department of Biosciences, Åbo Akademi University, Turku, Finland c School of Biological Sciences, Monash University, Victoria, Australia article info Article history: Received 5 April 2013 Initial acceptance 10 May 2013 Final acceptance 30 July 2013 Available online 6 September 2013 MS. number: 13-00293R Keywords: body size egg predation nest building nest choice parental care Pomatoschistus minutus predation threat predatoreprey interaction reproduction cost sexual selection Nest defence is a particularly costly component of parental care. The costs of nest-related behaviours are affected by the nest’s location, size and architecture; yet surprisingly little is known about how choice of a nesting site or nest characteristics are adjusted as a response to the threat of future nest predation. To address this topic, we investigated whether egg predation threat influenced nest choice and nest con- struction in the sand goby, Pomatoschistus minutus, a small marine fish with exclusive paternal egg care. We found that exposure to sand shrimp, Crangon crangon, a predator of sand goby eggs, did not affect male preferences for large nesting resources or the onset of nest-building activity. Small and large males did, however, respond differently to the presence of shrimp during the nest-building phase. In particular, large males used more sand to cover their nests in the shrimps’ presence. By contrast, neither the presence of egg predators nor male size class affected the size of the nest entrance. Together, our results show that while the risk of future egg predation may not necessarily influence a male’s decision to nest, during the nest construction phase it can nevertheless induce responses that strongly depend on builder phenotype. Ó 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Looking after young is often costly in terms of survival rate or lost mating opportunities (Gross & Sargent 1985; Clutton-Brock 1991; Smith & Wootton 1995). The costs of parental activities are especially acute when it comes to defending a nest against would- be predators (Ghalambor & Martin 2001). In birds, for instance, parents incur higher costs from defence of chicks than from nest building or incubation (Owens & Bennett 1994). Similarly, in an egg-guarding fish, the smallmouth bass, Micropterus dolomieu,a higher abundance of nest predators was associated with markedly increased metabolic costs during egg guarding (Steinhart et al. 2005). In this respect, nest characteristics may, at least in some species, influence both the level of protection afforded to devel- oping eggs or juveniles and the costs incurred by parents (Canali et al. 1991; Hoi et al. 1994; Bult & Lynch 1997; Jones & Reynolds 1999a; Petit et al. 2002; but see also Burhans & Thompson 1998). For instance, northern flicker, Colaptes auratus, nests that were higher up above the ground and more concealed by vegetation around the nest cavity entrance were better protected against predation (Fisher & Wiebe 2006). Likewise, in hole-nesting bees and wasps, nest density, nest position and nesting behaviour can all affect the vulnerability of nests to parasites (Rosenheim 1989; Coster-Longman et al. 2002; Polidori et al. 2010). In fish, nest ar- chitecture can also affect the dissolved oxygen levels inside the nest and, in so doing, influence the cost of male egg care (Takegaki & Nakazono 2000). Nevertheless, despite the importance of nest location and nest architecture on offspring survival, surprisingly little is known about how the choice of nest site by parents or, indeed, adjustment of nest characteristics, is influenced by the future threat of nest predation. The sand goby, Pomatoschistus minutus, is an excellent model organism for investigating the effects of predators on nesting be- haviours because nesting decisions are an important determinant of offspring survival as well as female mate choice (e.g. Lindström & Ranta 1992; Svensson & Kvarnemo 2003, 2005; Lehtonen et al. 2010). Males of this small, benthic marine fish build nests under empty shells or flat rocks by piling sand on top of, and excavating under, the resource, leaving a single narrow nest opening. Males * Correspondence: T. K. Lehtonen, Section of Ecology, Department of Biology, University of Turku, 20014 Turku, Finland. E-mail address: topi.lehtonen@utu.fi (T. K. Lehtonen). Contents lists available at ScienceDirect Animal Behaviour journal homepage: www.elsevier.com/locate/anbehav 0003-3472/$38.00 Ó 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.anbehav.2013.08.005 Animal Behaviour 86 (2013) 867e871