Spatiotemporal resource distribution and foraging strategies of ants (Hymenoptera: Formicidae)

Abstract

The distribution of food resources in space and time is likely to be an important factor governing the type of foraging strategy used by ants. However, no previous systematic attempt has been made to determine whether spatiotemporal resource distribution is in fact correlated with foraging strategy across the ants. In this analysis, I present data compiled from the literature on the foraging strategy and food resource use of 402 species of ants from across the phylogenetic tree. By categorizing the distribution of resources reported in these studies in terms of size relative to colony size, spatial distribution relative to colony foraging range, frequency of occurrence in time relative to worker life span, and depletability (i.e., whether the colony can cause a change in resource frequency), I demonstrate that different foraging strategies are indeed associated with specific spatiotemporal resource attributes. The general patterns I describe here can therefore be used as a framework to inform predictions in future studies of ant foraging behavior. No differences were found between resources collected via short-term recruitment strategies (group recruitment, short-term trails, and volatile recruitment), whereas different resource distributions were associated with solitary foraging, trunk trails, long-term trail networks, group raiding, and raiding. In many cases, ant species use a combination of different foraging strategies to collect diverse resources. It is useful to consider these foraging strategies not as separate options but as modular parts of the total foraging effort of a colony.

Keywords: Review; collective behavior; evolution; framework; group recruitment; honeydew; networks; pheromone; phylogeny; trunk trails.

Fig. 1

Foraging strategies of ants.

Fig. 2

Long trunk trails of the seed harvesting ant Pheidole xerophila Wheeler, 1908. Trunk trails radiating out from the nest on the small hill in the background are traced out on the ground with fluorescent orange flagging. This colony harvests seeds in the highly patchy environment at the edge of the Willcox playa in Arizona (USA), crossing areas of salt flats to reach patches of grass. Photo by M. Lanan.

Fig. 3

The distribution of food types and foraging strategies across the phylogeny of the ants. The genus-level phylogeny is drawn to reflect the current understanding of the ant phylogenetic tree based on recently published molecular studies (Brady & al. 2006, Moreau & al. 2006, Lapolla & al. 2010, Mehdiabadi & Schultz 2010, Ward & al. 2010, Schmidt 2013). Use of each food type within a genus is indicated with colored rectangles, while occurrence of foraging strategies within a genus are indicated with solid circles. Possible, but uncertain occurrence of a foraging strategy is indicated with open circles. References for the diet and foraging data are provided in Table S1. In addition, Figure S1 in the Supplemental Information presents a more detailed, larger version of this phylogeny with taxa names.

Fig. 4

The spatiotemporal distribution of food resources collected by a) solitary foraging, b) group recruitment, c) short-term trails, d) volatile recruitment, e) group raiding, f) raiding, g) trunk trails, h) long-term trail networks, i) polydomy, and j) nomadism. Axes of the graphs are explained in Table 1, with the fourth axis, size, represented by color. Spheres represent the mean and standard deviation of the data for each axis. Small black points on the walls of the graph represent individual data points for which data on two dimensions was available. Data sources are listed in Table S2.

Fig. 5

The types of food collected by a) solitary foraging, b) group recruitment, c) short-term trails, d) volatile recruitment, e) group raiding, f) raiding, g) columns and fans, h) trunk trails, and i) long-term trail networks. Only data for which a particular food type was described as being gathered with a particular foraging strategy were included. Prey are defined as large if they require more than one ant to retrieve.

Fig. 6

a) A solitary forager of Dorymyrmex bicolor Wheeler, 1906 retrieves a dead insect from a dry riverbed near Tucson, Arizona (USA). b) Multiple Crematogaster sp. workers tend a group of aphids on a grass stem at Reddington Pass, Arizona (USA). Photos by M. Lanan.

Fig. 7

Two examples of unusual combinations of foraging strategies used by ants. a) Forelius pruinosus (Roger, 1863) uses a long-term trail network linking multiple nests where workers tend root coccids, and workers also search for dead insects along fans and columns that radiate outward from the network. A short-term trail is also used to collect vertebrate carrion (a dead baby bird) (M. Lanan, unpubl.). b) Pheidologeton diversus (Jerdon, 1851) uses a combination of trunk trails, short-term trails, and swarm raids (redrawn from Moffett 1988b; reproduced with permission from publisher).