Seasonal Count of Nile Crocodiles
Date: 28 June and 26 July 2009
Requesting organisation: Xander Combrink of the School of Biological & Conservation Sciences at UKZN
Location: Lake Sibaya, KwaZulu Natal
Pilot: Donovan Barton-Hobbs and Daryl Kimber
Early in 2009 the Bateleurs was approached by Xander Combrink of the School of Biological & Conservation Sciences at UKZN, to assist with a series of aerial surveys for researchers conducting seasonal counts of Nile Crocodiles.
The first of these counts took place on two different days. The first day of the survey was flown at Lake Sibaya (see photo above) in June, by Bateleurs pilots Donovan Barton-Hobbs and Daryl Kimber, but weather conditions were unfavourable and it was decided to repeat the survey in July. The second day of this survey was flown, again, by Donovan Barton-Hobbs. Here are some extracts from the detailed report compiled by researchers Xander Combrink and Dr Ricky Taylor, the full report is available on request.
Report by Xander Combrink
“We conducted an aerial count for crocodiles at Lake Sibaya on 28 June 2009, using two pilots and two airplanes. Six individuals were counted and this result seemed to indicate a significant decrease in the population, compared to the 22 crocodiles counted in June 2007. However, there was a moderate to strong wind (40km/h) on the day and windy conditions often result in crocodiles seeking shelter amongst vegetation/reeds, so it was decided to repeat the survey under more favourable weather conditions.
Accordingly, we repeated the survey on 26 July 2009, departing from 121/Dukuduku and surveying the lake in a clockwise direction. Seven crocodiles were counted, one more than during the previous count a month earlier (28 June 2009). This result is surprising – counting conditions were perfect, so almost 90% of the counted crocodiles were basking, compared to 20% during the windy June survey. The distribution of the observed crocodiles in Lake Sibaya seems to coincide with areas of relative little human disturbance/development (settlements). Surprisingly, no crocodiles were counted along the eastern shoreline which used to be a favoured area for adult crocodiles.
An alarming decrease in numbers
During the first aerial survey in 1985, 67 crocodiles were counted. This figure increased to 107 individuals in 1990 but the period 1990 – 1993 saw a sharp decrease in numbers to 53 crocodiles. Since 1993 the observed population has decreased steadily to the seven individuals counted during July 2009. The decrease in the number of crocodiles at Lake Sibaya is linked to the increasing human population around the lake, with a consequential increase in demand for more natural resources (e.g. water, food, building material), more livestock and fishing activities with subsequent disturbance to nesting and basking crocodiles, increased agricultural activities, gillnet mortalities of young crocodiles, baited snare traps, the destruction of crocodile nesting sites and removal of eggs, killing of crocodiles due to perceived/real threat to humans and livestock and the demand for crocodile fat, blood and other organs in the traditional medicine market.
Agriculture and tourism
It seems that agricultural activities have expanded around the lake since the previous aerial survey. Much of this focussed at the inlets of the numerous dendritic arms of the lake. The subsequent replacement of aquatic vegetation with crops will impact negatively on the abundance and diversity of animals found in these habitats. Also, as a result of the decreasing lake level, numerous vehicle tracks and a few vehicles were seen along the eastern shoreline of the lake. Five touring canoes (see photo above) were seen in the Mabibi area, which suggests the possibility of a canoe tour operator active in the area.
In light of the aforementioned pressures on the remaining crocodiles in the lake, it is unlikely that the population will recover without a long term strategy that takes into account ecological/conservation, and social as well as economic considerations.
Many thanks to The Bateleurs and especially pilots Donovan Barton-Hobbs and Daryl Kimber, who made it possible to do the two flights for this survey.”