Natural history, population changes, and conservation needs of the Guacharaquita frog Tachiramantis lentiginosus (Anura, Strabomantidae) in the Colombian Andes. Tachiramantis is a recently proposed genus that includes seven species, four considered threatened with a declining trend, while three lack sufficient data for conservation assessment. The Guacharaquita frog Tachiramantis lentiginosus is one of these species, with substantial information gaps regarding its natural history, threats, and population density changes, particularly in isolated populations such as that studied here. In San Antonio, the only location in Colombia where T. lentiginosus is found, we evaluated changes in population density and vegetation cover over 10 years (2014-2024). Additionally, we mapped current threats and describe key aspects of microhabitat use and activity patterns. Analyses were conducted using the Kruskal-Wallis test, and Global Forest Change Analysis. Our findings reveal a significant decline in population density and vegetation cover, with agriculture, cattle ranching, and mining identified as major threats. We also observed variable microhabitat use and a distinct activity period, suggesting the species lacks specific microhabitat preferences and is primarily nocturnal. We conclude that this only known population in Colombia is in decline, facing severe threats that fragment its forest habitat and contribute to cover loss.