By Betty Mutheu - Ms. Mutheu is a student at Egerton University in Kenya and is currently interning with Wildlife Works.
In the world of ecological research, scientists and students employ various methods to conduct biodiversity censuses and compare ecosystems. These methods are carefully chosen based on the purpose of the census, the species of interest, scientific rigor, and practicality. Among these techniques, the transect method stands out as a crucial tool for understanding our ecosystems.
A transect is a sampling method that involves following a linear path across a specific area to study the abundance and distribution of different species. Scientists strategically design transects to randomly sample populations, ensuring comprehensive coverage while minimizing bias.
At the Kasigau Corridor REDD+ Project (KCRP) in Kenya, transects play a vital role in monitoring biodiversity across the vast 500,000-acre area. The 43rd session of KCRP’s project-wide wildlife monitoring road transects, led by biodiversity scientist Bernard Amakobe, concluded in mid-July. The 27 permanent road transects, each 10-15 km long, were set up within both the project accounting and reference areas. Each session, taking about 10 days to complete, has been conducted quarterly since the project’s inception. The transects protocol involves driving along the transect slowly while 2 observers sitting on either side of the vehicle scan the area for wildlife. When an animal or group of animals are observed, the vehicle stops immediately.
A laser rangefinder measures the distance to the point where the animal was first observed. The vehicle’s location is recorded on a GPS, alongside the time of observation, species, number of individuals and the perpendicular distance between the transect and the observation. The road transect dataset has been essential in documenting the high conservation value species in the project area and is also important in understanding wildlife dynamics.
The project area boasts an impressive array of wildlife, including over 300 bird species, 20 bat species, and more than 50 large mammal species. Among these are threatened species recognized by the International Union for Conservation of Nature Red List, such as the Grevy's Zebra and African Wild Dogs. In the latest sampling, some of the highlights were endangered secretary birds, the rare Kori bustard, and a family of three adult and four juvenile lions.
KCRP’s data collection occurs four times per year, capturing both dry and wet seasons, and continues throughout the project's lifespan. This ongoing monitoring enables scientists to track changes over time and provides valuable insights for managers and policymakers to make informed decisions.
Night transects are particularly crucial for observing nocturnal animals such as leopards, owls, aardvarks, aardwolves, and cheetahs. These elusive creatures are often spotted by the telltale glow in their eyes when illuminated by powerful torches.
The transect data serves multiple purposes beyond wildlife monitoring. It aids in tracking deforestation rates within the project area and provides essential information for managers of the eco-charcoal project. This data helps in devising strategies to encourage communities to adopt eco-charcoal as an alternative to traditional charcoal, which contributes to deforestation.
To estimate wildlife populations from these transects, scientists employ a sophisticated data analysis method called distance sampling. This technique calculates species density using a detection function based on observations along the transect line. For each animal spotted, whether alone or in a group, scientists record its identity, total number, distance from the transect line, and GPS coordinates. This information allows researchers to estimate population densities of different species in the study areas and potentially document new species ranges or habitats.
While transect surveys offer numerous advantages, such as covering large areas systematically and providing standardized data collection for easy comparison between studies, they are not without limitations. Observer bias based on detection ability and decreased probability of animal detection at greater distances are challenges that researchers must account for. To complement transect surveys, the Kasigau Corridor Project also employs additional monitoring techniques. These include regular monitoring of invasive species like the Indian house crow, charcoal transects along the Nairobi-Mombasa highway, and the use of camera traps for less intrusive observation of wildlife in their natural habitats.
By employing these diverse monitoring techniques, the Kasigau Corridor Project generates invaluable data on species distribution and population trends. This information is crucial for informing conservation efforts, guiding ecosystem management decisions, and serving as a reference for future ecological studies. As we continue to face environmental challenges, the insights gained from transect surveys and other monitoring methods will play an increasingly important role in protecting and preserving our planet's biodiversity.
