Food Habits of the Silky Anteater (Cyclopes didactylus) in the Central Amazon

Abstract

The silky anteater ranges widely throughout Central and South America, yet it has been little studied due to the difficulty of locating it. The smallest of the anteaters, it is nocturnal and arboreal (Sunquist and Montgomery, 1973; Montgomery, 1979; Wetzel, 1982) and is reported to feed on ants, termites, and coccinellid beetles (Beebe, 1918; Montgomery, in press; Vesey-Fitzgerald, 1936). We analyzed four fecal samples from four Cyclopes that were brought by locals to our laboratory at the Instituto Nacional de Pesquisas da Amazonia (INPA), in Manaus, Brazil. As Cyclopes are reported to defecate approximately once daily (Merritt, 1971), such samples should be representative of the previous night's foraging. Fecal samples were preserved dry and then washed in 70% alcohol to simplify the sorting process. For each sample, heads of arthropods were separated from other body parts using a dissecting microscope, and grouped into morpho-species based on size and shape characters. A simple size-index was used (head length + width) to give a physical dimension to the numerical frequency data. Similar techniques have been used in other studies of insectivore food habits (e.g., Calver and Wooler, 1982). The feces contained almost no intact arthropods, but large quantities of legs, heads, antennae and other parts of exoskeletons were present. As these parts showed no degradation by digestive processes, we assume that Cyclopes does not possess either chitinase or chitobiase, digestive enzymes known from bats (Jeuniaux, 1961). Total counts of insects per fecal sample ranged from 95 to 7,743 and, with the exception of 6 coleopterans in one sample, all the arthropods found were hymenopterans, primarily ants (Formicidae). We were able to separate the ants into 79 morpho-species and 9 genera (Table 1). Due to the complex taxonomy of some of these genera, it was impossible to determine species and many of these morpho-species may represent various castes (i.e., worker, soldier, etc.) of a single species of ant. Four genera accounted for 95.5% of the 10,514 ants in the combined samples. These were Crematogaster (72.3%), Zacryptocerus (11.2%), Pseudomyrmex (7.2%), and Camponotus (4.2%). Other genera such as Solenopsis, Pheidole, Procryptocerus, etc. accounted for only a small part of the sample (total = 2.0%), as did unidentified Hymenoptera (2.6%) and Coleoptera (0.1%). These results are very similar to those of Montgomery (in press) who found that Cyclopes in Panama fed primarily on the genera Crematogaster, Solenopsis, and Pseudomyrmex. When expressed in terms of our size-index, the same pattern persists. However, the relative importance of Zacryptocerus was higher (38.7% versus 11.7%) due to the large size of this genus. Metabolic rates of Cyclopes have been measured (McNab, 1982) and are low in comparison with the mammalian metabolic standard. Assuming a single daily defecation, our animals ate 100 to 8,000 ants per