The mating behavior of several anteater species has been documented under zoo conditions (Sanmarco, 1985; Moeller, 1990; Coleman, 2003), but observations have yet to be made in the wild. No descriptions have been published on the mating behavior of Tamandua mexicana under any conditions, although it is the most common anteater in Central America (Lubin, 1983).
Northern tamanduas are medium-sized animals (4–6 kg) that feed on ants and termites (Montgomery, 1985a, 1985b); they range from eastern Mexico to northwestern Venezuela, Colombia, Ecuador and Peru (Wetzel, 1975, 1982, 1985; Fonseca and Aguiar, 2004). Macdonald (1995) speculated that T. mexicana may mate in the fall, but the few reports available suggest that mating is aseasonal (Lubin, 1983). Estrus cycles have not been reported for T. mexicana, but its close relative T. tetradactyla has estrus cycles lasting between 35 and 42 days (Sanmarco, 1987; Hay et al., 1994). Silveira (1969) reported that gestation in tamanduas is approximately 130–150 days, but data from a zoo birth of T. tetradactyla suggests that gestation could be as short as 85 days (Sanmarco, 1987). T. mexicana are solitary but their home ranges, which are approximately 25 ha (Montgomery, 1985b), may overlap (Lubin et al., 1977).
While hiking on a beach in Corcovado National Park, Costa Rica (08°29′N, 83°36′W), at 11:21 hrs on 1 February 2005, I witnessed a pair of T. mexicana engaging in mating behavior. Standing at a distance of five meters, I observed the pair interacting for over five minutes, during which two copulations occurred.
As I approached, I noticed one tamandua (later assumed to be female) searching for insects on top of a fallen log, which protruded onto the beach from beneath the shadowed understory of the forest. A second tamandua (later assumed to be male) emerged from the forest along the top of the same log. When the male encountered the female he first smelled her rump, and then followed her while she searched for insects, pacing back and forth on the log several times. As the male followed the female he swatted her rump with his forelimbs (Fig. 1a), and on several occasions he straddled the female and scrambled over her.
He then turned to face her, grabbing and holding her head for a short time (Fig. 1b), and then scrambled over her again. Both tamanduas remained on top of the log during the entire encounter, foraging and feeding on insects. The female acted antagonistically towards the male, attempting to avoid and flee from him. Twice both tamanduas reared up on their back legs facing each other, aggressively swinging their foreclaws (Fig. 1c). Several times the tamanduas paused to sniff each other's noses for 5–10 seconds (Fig. 1d). Twice the male mounted the female dorsally, despite her attempts to flee, and achieved copulations. Each copulation was brief (10–30 seconds) with approximately two minutes between them.
During the first copulation, the male mounted the female on top of the log and used his forelimbs to restrain her by holding her neck and forelegs (Fig. 1e). The second time the male mounted the female as she attempted to dismount the log. He grabbed her with his forelimbs, holding the log with his prehensile tail, and mounted her on the side of the log (Fig. 1f). Finally the male straddled the log and slid down the length of its incline, walking into the forest and leaving my field of view. The female continued to search for insects on the fallen log for another eight minutes before departing into the forest as well.
The dorso-ventral mating behavior of Tamandua mexicana is different from the behavior typical of at least two other Neotropical xenarthrans. The twotoed sloth (Choloepus didactylus) mates in a ventralventral manner (Burton, 1976) and giant anteaters (Myrmecophaga tridactyla) mate with the female lying on her side (Moeller, 1990). However, other aspects of the mating behavior of the giant anteater are consistent with my observations of T. mexicana. The male giant anteater follows the female during courtship and occasionally paws and sniffs her, while both sexes continue to forage and feed (Shaw et al., 1987). Like during courtship the male and female exchange blows and pinches (Moeller, 1990), and engage in “face-to-face embraces” similar to T. mexicana (Coleman, 2003). The onset of aggression and copulation seem to coincide in Tamandua tetradactyla (Meritt, 1976), as observed here with T. mexicana. Mating in T. tetradactyla is preceded by both sexes engaging in mutual inspection, “gentle boxing,” cuddling, and following each other; a male T. tetradactyla will show interest in a female by sniffing, grooming, and following her (Sanmarco, 1985).
These observations of T. mexicana suggest that the strong forelimbs and tail may aid males in copulating with unwilling females. The prehensile tail provides stability during arboreal locomotion (Montgomery and Lubin, 1977; Lubin, 1983) but it may also aid in stabilizing the males during mating. Taylor (1978, 1985) has discussed the functional morphology of the tamandua's powerful forelimbs in the context of opening termite mounds, but my observations suggest that the forelimbs may also play a role in a male's ability to manipulate the position of the female during mating. Northern tamanduas find their prey by scent (Montgomery, 1985), and my observations suggest that scent may also be important during mating, perhaps to identify potential mates and assess their receptivity. The male T. mexicana may have been scent-marking both the female when he scrambled over her, and the log when he slid down it. I was unable to find additional information on scent glands and scent-marking in tamanduas for comparison. To my knowledge this is the first account of mating behavior in T. mexicana and the first account of any anteater mating in the wild.
Bob Timm and Larry Gilbert gave helpful advice, while Carlos Garcia-Robledo assisted with making the figure. This manuscript was improved by comments from Tanya Hawley. Logistical support in Costa Rica was provided by MINAE, especially Wendy Barrantes, and Friends of the Osa.
 David Matlaga, Department of Biology, University of Miami, P.O. Box 249118, Coral Gables, Florida 33124, USA e-mail: <email@example.com>