Extreme Behavioral Adjustments by an Orb-Web Spider to Restricted Spaces

Adaptive phenotypic flexibility occurs in many traits in many different organisms and has profound evolutionary consequences (West-Eberhard 2006). Spider orb-web construction behavior exemplifies complex, highly stereotyped, relatively innate behavior whose details can nevertheless be adjusted to some extent to local conditions (Witt et al. 1968; Vollrath 1992; Heiling & Herberstein 2000), and the former perception of stereotypy in orb design is currently being replaced by the realization that details of orb design are extremely flexible (Herberstein & Tso 2011). There is a long list of variables that are known to induce orb weavers to modify orb designs or that are at least correlated with differences in orb design. It includes the size and shape of the space available (LeGuelte 1966; Ades 1986; Leborgne & Pasquet 1987; Krink & Vollrath 2000; Harmer & Herberstein 2009; Hesselberg 2010), closed vs. open habitats (Blamires et al. 2007), gravity (LeGuelte 1966; Vollrath 1992; Herberstein & Heiling 1999), the amount of silk in the silk glands that spiders have to construct the web (Reed et al. 1970; Eberhard 1988a), the presence of other lines they have already built (Hingston 1920, 1922; Eberhard 1972; Gillespie 1987), previous overall foraging success (Higgins 1992; Vollrath 1992; Sherman 1994; Herberstein & Heiling 1999; Herberstein et al. 2000) and also localized success in different parts of the web (Heiling & Herberstein 2000), body weight (Herberstein & Heiling 1999), impending molt or oviposisiton (Higgins 1990; Sherman 1994), recent memories of distances and directions they have moved (Eberhard 1988b; W. G. Eberhard & T. Hesselberg, submitted), weather conditions and previous rainfall (and thus damage to the previous web) (Cangialosi & Uetz 1987; Higgins & Buskirk 1992), predation risk (Higgins 1992), and to the type of prey available (Sandoval 1994). Orb weaving spiders may be unusual among invertebrates in that they take into account unusually large numbers of stimuli in Correspondence Gilbert Barrantes, Escuela de Biologı́a, Universidad de Costa Rica, Ciudad Universitaria Rodrigo Facio, San José, Costa Rica, CP 2060. E-mail: [email protected]