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So, how many elephants is too many elephants? It's a question people have wrestled with for ages. Kruger National Park, home to one of Africa's largest elephant populations, has seen their numbers grow from just a handful in the early 1900s to over 31,000 by 2020. That's a lot of elephants! A recent study using smarter aerial surveys and fancy math gives us a more clear picture of just how fast these gentle giants are multiplying. Turns out, since 2013, their numbers have been growing by about 5.3% each year.

The rapid improvement of camera traps in recent decades has revolutionized biodiversity monitoring. Despite clear applications in conservation biology, camera traps have seldom been used to model the abundance of unmarked animal populations. The goals of this review are to summarize the challenges facing abundance estimation of unmarked animals, present an overview of existing analytical frameworks, and provide guidance for practitioners seeking a suitable method.

1. Spatially explicit capture–recapture methods use data from the detection of marked animals at known points in space to estimate animal population density without bias from edge effects. Detection is by means of stationary devices such as traps, automatic cameras or DNA hair snags. Data collection is often expensive, and it is not obvious how to optimize the frequency of sampling and the spatial layout of detectors.

African elephants (Loxodonta africana) are imperiled by poaching and habitat loss. Despite global attention to the plight of elephants, their population sizes and trends are uncertain or unknown over much of Africa. To conserve this iconic species, conservationists need timely, accurate data on elephant populations. Here, we report the results of the Great Elephant Census (GEC), the first continent-wide, standardized survey of African savannah elephants. We also provide the first quantitative model of elephant population trends across Africa.