Army ants in four forests: geographic variation in raid rates and species composition

Abstract

Summary1. The New World army ants are top predators in the litter of tropical forest, but no comprehensive studies exist on variation in assemblage-wide activity and species composition. We used standardized protocols to estimate foraging raid rates and species composition of army ant communities in four Neotropical forests. The study sites spanned approximately 10 ° latitude, with two sites each in Central and South America. 2.We recorded a total of 22 species of army ants. The four sites varied in observed and estimated species richness. Species overlap was highest between the Central American sites, and lowest between the South American sites. 3. Raid activity varied significantly among sites. Raid activity per kilometre of trail walks was over four times higher at the most active site (Sta. Maria, Venezuela) than at the least active site (Barro Colorado Island, Panama). Furthermore, each site showed a different diel pattern of activity. For example, raid activity was higher during daylight hours in Costa Rica, and higher at night in Venezuela. Raid activity relationships with ambient temperature also varied significantly among sites. 4. The overall rate of army ant raids passing through 1 m 2 plots was 0·73 raids per day, but varied among sites, from 0 raids per day (Panama) to 1·2 raids per day (Venezuela). 5. Primarily subterranean species were significantly more abundant in Venezuela, and above-ground foragers that form large swarm fronts were least abundant in Panama. The site heterogeneity in species abundance and diel activity patterns has implications for army ant symbionts, including ant-following birds, and for the animals hunted by these top predators.

First standardized inventory of ants (Hymenoptera: Formicidae) in the natural grasslands of Paraná: New records for Southern Brazil

“…The dearth of army ants in our samples reflects the fact that this group is primarily found in structurally more heterogeneous physiognomies, such as forests, and are usually less diverse and harder to observe in open fields and savannas (Baccaro et al, 2015). However, this result can also be due to short sampling period (see O'Donnell et al, 2007).…”

The effect of local dominance and reciprocal tolerance on feeding aggregations of ocellated antbirds

“…The activity of E. burchellii swarms declines in the afternoon at La Selva (O'Donnell et al 2007), so we collected nearly all samples before noon and recorded the hour in which each observation was made. The size (width) of the swarm can affect prey intake through competition (Willson 2004) and was visually estimated from the blind (to prevent disturbance) to the closest metre at the end of each observation period.…”

“…Weather conditions affect E. burchellii activity (O'Donnell et al 2007) and were measured during each sampling period by an automatic meteorological station (ambient temperature, precipitation and humidity). The activity of E. burchellii swarms declines in the afternoon at La Selva (O'Donnell et al 2007), so we collected nearly all samples before noon and recorded the hour in which each observation was made.…”

Subterranean ants (Hymenoptera, Formicidae) as prey of fossorial reptiles (Reptilia, Squamata: Amphisbaenidae) in Central Brazil

“…We know very little on the biology of Cheliomyrmex species; O'Donnell et al (2005) reported that C. andicola prey on large-bodied ground dwelling invertebrates and, probably, vertebrates, using (possibly) their unusual mandibles and stings to pierce and grip the integument of non-arthropod prey animals, and for rapidly subduing large-bodied prey, respectively. Despite the abundance of Ecitoninae in Neotropical forests (Kaspari & O'Donnell, 2003), data on the structure of their communities and ecological impacts are limited (O'Donnell et al, 2007, but see Berghoff et al, 2008, and included references for Panama's Canal Zone). Most of what is known about the biology of Ecitoninae is derived from observations on the behavior of Eciton burchelli (see Gotwald, 1995;O'Donnell et al, 2007).…”

“…Despite the abundance of Ecitoninae in Neotropical forests (Kaspari & O'Donnell, 2003), data on the structure of their communities and ecological impacts are limited (O'Donnell et al, 2007, but see Berghoff et al, 2008, and included references for Panama's Canal Zone). Most of what is known about the biology of Ecitoninae is derived from observations on the behavior of Eciton burchelli (see Gotwald, 1995;O'Donnell et al, 2007).…”