Semen characteristics, handling of a highly viscous ejaculate, and exploratory cryopreservation attempts in free-ranging peri-urban giant anteaters (Myrmecophaga tridactyla)

Abstract

The giant anteater (Myrmecophaga tridactyla) is a vulnerable xenarthran with a wide geographic distribution across South and Central America. Reproductive data for this species remain scarce, particularly from free-ranging individuals in anthropogenically modified landscapes. This exploratory study describes semen characteristics and cryopreservation trials in free-ranging peri-urban giant anteaters admitted to a wildlife hospital following vehicle collisions or wildfire burns in São Paulo state, Brazil. Five adult males were assessed; median body mass was 35.80 kg (IQR 3.75), body temperature 34.5 °C (IQR 0.30), and haematocrit 30.4% (IQR 4.30). Semen was collected by electroejaculation in four of the five animals, the day after the admission. All samples were markedly viscous (grade 4/4), and five viscosity-reduction methods were compared descriptively; filtration followed by fine-needle aspiration performed best in this small sample size condition. Median seminal volume was 8.5 mL (IQR 10.5), progressive motility 25.0% (IQR 31.25), and sperm concentration 126.0 × 10⁶ sptz/mL (IQR 77.63), while total morphological defects reached 83.54% (IQR 17.81). Two samples were cryopreserved using a commercial egg yolk-Tris based extender (BotuBov®) containing 6.4% glycerol. Post-thaw evaluation revealed progressive motility of 5% in one sample, while no motile spermatozoa were recovered from the remaining one. These results document the challenges of cryopreserving giant anteater semen using a bovine extender and highlight the need for species-specific protocols. Despite the poor cryo-survival, this study contributes baseline reproductive data from an underrepresented context, free-ranging, injured, peri-urban individuals, and showcases the possibility of opportunistic semen collection for building germplasm banks for this threatened species.