Quantitative assessment of ticks in a hot cave in the Amazon reveals that the genus Antricola (Ixodida: Argasidae) has the highest cave tick population density on planet

Within Argasidae ticks, the genus Antricola is restricted to the New World and exhibits a unique biology: only larvae are hematophagous and parasitize bats, whereas nymphs and adults are free-living and supposedly to feed on bat guano in hot caves with high temperatures (30-38 °C) and relative humidity close to 100%. This study quantified the tick population in an Amazonian hot cave located in the Natural Park of Porto Velho (Rondônia, Brazil), inhabited by thousands of insectivorous bats. Standardized guano samples (100 cm² at 10 points) were collected during dry and rainy seasons and examined in the laboratory. The guano-covered area totaled 146.34 m². A total of 7,388 ticks was collected in the dry season and 8,753 in the rainy season, with more than 99% belonging to Antricola, mainly A. delacruzi. The estimated mean density was 80,705 ticks/m², corresponding to an approximate population of 11.8 million individuals on the cave floor-the highest tick density ever recorded in a cave worldwide. Only nymphs and adults were found, suggesting that Antricola eggs and larvae remain in wall crevices, and that rapid larval development, combined with continuous guano feeding, promotes long post-larval longevity. These findings highlight a highly specialized host-parasite dynamic and emphasize the importance of conserving Amazonian cave ecosystems and surrounding forests, which are threatened by deforestation and other anthropogenic pressures.