Fifty+ years of primate research illustrates complex drivers of abundance and increasing primate numbers.

Many primate populations are threatened by human actions and a central tool used for their protection is establishing protected areas. However, even if populations in such areas are protected from hunting and deforestation, they still may be threatened by factors such as climate change and its cascading impacts on habitat quality and disease dynamics. Here we provide a long-term and geographically wide-spread population assessment of the five common diurnal primates of Kibale National Park, Uganda. Over 7 year-long or longer census efforts that spanned 52 years, our team walked 1466 km, and recorded 480 monkey groups. Populations were generally relatively stable with a few exceptions, for which no apparent causative factors could be identified. This stability is unexpected as many ecological changes documented over the last 34+ years (e.g., decreasing food abundance and quality) were predicted to have negative impacts. Populations of some species declined at some sites but increased at others. This highlights the need for large, protected areas so that declines in particular areas are countered by gains in others. Kibale has large areas of regenerating forest and this most recent survey revealed that after 20+ years, forest regeneration in many of these areas appears sufficient to sustain sizeable primate populations, except for blue monkeys that have not colonized these areas. Indeed, the average primate abundance in the regenerating forest was only 8.1% lower than in neighboring old-growth forest. Thus, park-wide primate abundance has likely increased, despite many pressures on the park having risen; however, some areas in the park remain to be assessed. Our study suggests that the restoration, patrolling, and community outreach efforts of the Uganda Wildlife Authority and their partners have contributed significantly to protecting the park and its animals.

Vertebrate environmental DNA from leaf swabs.

Terrestrial vertebrates are threatened by anthropogenic activities around the world. The rapid biodiversity loss that ensues is most intense in the tropics and affects ecosystem functions, such as seed dispersal, or may facilitate pathogen transmission1. Monitoring vertebrate distributions is essential for understanding changes in biodiversity and ecosystems and also for adaptive management strategies. Environmental DNA (eDNA) approaches have the potential to play a key role in such efforts. Here, we explore whether eDNA swabbed from terrestrial vegetation in a tropical biodiversity hotspot is a useful tool for vertebrate biomonitoring. By swabbing leaves, we collected eDNA from 24 swabs at three locations in Kibale National Park, Uganda and used two metabarcoding systems to catalog the vertebrate taxa in the samples. We detected 52 wild vertebrate genera, including 26 avian and 24 mammalian genera; 30 of these assignments could be refined to the species level. We detected an average of 7.6 genera per swab. This approach, with its inexpensive and simple collection and DNA extraction, opens the door for inexpensive large-scale vertebrate biomonitoring.