Abstract
North African desert ants, Cataglyphis fortis, use path integration as their primary means of navigation. The ants also use landmarks when these are available to improve navigation accuracy. Extended landmarks, such as walls and channels, may serve further functions, for example, local guidance or triggering of local vectors. The roles of such structures were usually examined in homing animals but not during food searches. When searching for familiar feeding sites, Cataglyphis may show intriguing deviations from expected search performances. These may result from the presence of extended landmarks, namely experimental channels. Here we scrutinise this hypothesis of landmark guidance in food searches. We prevented the ants from seeing the channel walls by covering their eyes, except the dorsal rim area. This experiment was repeated in the open test field with an alley of black cylinders to extend our findings to a more normal foraging environment. Ants with covered eyes did not deviate from expected search performances, whereas ants with normal eyes extended their searches along the axis of the leading structures by 15–20 %, in both channels and landmark alleys. This demonstrates that Cataglyphis orients along extended landmarks when searching for familiar food sources and alters its search pattern accordingly.
Highlights
Cataglyphis fortis (Wehner 1983) ants live in the salt flats of North Africa
Since Cataglyphis species do not use pheromone trails, these routes have to be defined by other means, namely by visual structures along the trail. These visual cues are employed for navigation in North African Cataglyphis species, as well as in Australian Melophorus bagoti, in South African Ocymyrmex and in other hymenopterans (Collett and Rees 1997; Collett et al 2002, 2007; Zeil et al 2003; Collett and Collett 2002, 2009; Cheng et al 2009; Graham and Cheng 2009; Wehner 2009; Collett 2010, 2012; Philippides et al 2011)
In our experiments we reproduced the intriguing shift in food searches observed in Cataglyphis foragers that were familiar with a feeder located in a channel set-up (Bolek et al 2012b) (Fig. 2e, f; grey box-and-whisker plots at bottom of each density plot)
Summary
Due to yearly winter flooding, these sabkhas are level, bare and virtually devoid of landmarks In this environment C. fortis ants rely on vector navigation as their primary means of navigation. Since Cataglyphis species do not use pheromone trails, these routes have to be defined by other means, namely by visual structures along the trail These visual cues are employed for navigation in North African Cataglyphis species, as well as in Australian Melophorus bagoti, in South African Ocymyrmex and in other hymenopterans (Collett and Rees 1997; Collett et al 2002, 2007; Zeil et al 2003; Collett and Collett 2002, 2009; Cheng et al 2009; Graham and Cheng 2009; Wehner 2009; Collett 2010, 2012; Philippides et al 2011). We present experiments suggesting that Cataglyphis uses channel-like structures and extended landmark arrays in navigation towards and in search for familiar food sources
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