Researcher: Dr. Michael Chase
BackgroundBetween 1982 and 2009, the Savute Channel was dry and the Botswana Department of Wildlife and National Parks pumped artificial water points at the heart of the Chobe National Park. This is no longer necessary as flow resumed in May 2009. The main aim of this project – run by the NGO Elephants Without Borders – is to determine the effects of water availability in the Savute Channel on elephant movements in the wake of flow resumption.
In 1957, after 70 dry years, the Savute Channel began to flow, entering the Mababe Depression (once a huge lake). During the flow years that followed, the Savute Channel’s water levels remained constant, filled with water from the distant catchment areas in Angola. When water in pans began to dry up, the animals turned to the channel for water.
In 1982, water in the Savute Channel and marsh began disappearing once more. The gradual draining away of water in the channel was attributed to lower flood levels. These in turn were attributed to lower rainfall in the Kwando-Linyanti Rivers, tectonic shift and blockages further up the Kwando River.
In an effort to bring relief to wildlife living in the region, the Department of Wildlife and National Parks (DWNP) drilled five boreholes to augment water through artificial waterholes. Today, a feature of Savute is its artificial waterholes and big elephant tuskers who seek refuge around these water points in the heart of Chobe National Park.
In May 2009, the Savute Channel started to flow again and by January 2010 water was entering the Savute Marsh. The Linyanti Swamps feed the Savute Channel which meanders in an easterly direction for some 100km until it reaches the Savute Marsh. The full channel now acts as a giant water trough running through the arid sands of Botswana’s northern Kalahari. Elephants now make use of this river along its entire length, from the Zibadianja Lagoon in the west to the Savute Marsh, feeding on the surrounding vegetation as they move.
The DWNP has therefore stopped providing water via the artificial waterholes due to the abundance of fresh water in the channel. This study will investigate the effects of recent flow and availability of water in the Savute Channel on elephant movements in the region.
With support received from the Wilderness Wildlife Trust this project will collar and monitor two elephants in the Savute region; recent developments in satellite technology mean that elephants can be monitored for periods of up to four years. This long-term spatial analysis will provide important information on the spatial ecology of elephants in this dynamic system.
- Collar two adult elephants with satellite collars.
- Record the seasonal movements of collared elephants.
- Determine the influence of water availability in the Savute Channel on the seasonal home ranges, distribution and movements of collared elephants.
- Compare the home ranges and seasonal movements of elephants when the Savute Channel was dry.
- Compare the movements of elephants in Savute Channel with those collared along the Boteti River (both systems previously dry and now have water).
- Provide monthly movement maps on the movements of elephants and reports to all stakeholders.
Two elephants (one bull and one cow) will be fitted with satellite collars in separate areas along the Savute Channel during September 2010. We will try to choose herds that are widely separated from each other to reduce the probability that the animals are members of the same clan. For family groups, we will target an older adult cow in the herd for collaring. Sub-adult and adult bulls will be identified for tagging in bull herds.
A helicopter will be used to locate and capture elephants for collaring. Elephants will be immobilised and then fitted with a satellite collar around the neck. The age of collared elephants will be determined using shoulder height.
Collared elephants will be tracked for four years. The duty cycle of the units will be set to download one GPS fix each hour. All units are equipped with a VHF transmitter, allowing periodic tracking of the collared elephant and retrieval of the unit.
Home range sizes will be estimated using the minimum convex polygon (MCP) and the fixed kernel (FK) methods. We will calculate the annual home range (wet and dry season ranges combined), and wet and dry season ranges
March / April 2012
CH46 “Scout” has been within the vicinity of King’s Pool, since her collaring, stretching her home range between Savute, Linyanti and across into the Selinda. She is seen on a regular basis.
CH48 “Atticus” is paralleling his exact movements of last season at this time of year, down to the exact same paths. For the first 3 months of the year, he spends most of his time on the sand-ridge above the Mababe depression and then moves into NG18, however only in a very tight range. Last year, he stayed within this tight “clump” for over two months. We’ll see if it changes this year.
CH53 “Chloe” and CH55 “Rosy”, the Chief Island females have moved onto different areas of the island, however, too have very limited ranges. At the moment, one of the donor’s family is at Mombo and believes the team is trying to track CH53 despite her in a “marshy” area. Let’s hope they succeed!
Annual Report – 2011
After 27 dry years, in May 2008, the Savute Channel started to flow again and by January 2010, water was entering the Savute Marsh. Elephants now make use of this river along its entire length, feeding on the surrounding vegetation as they move between the Mababe Depression and the Linyanti River.
This study, a collaboration between the Trust and the Botswana-based conservation charity Elephants Without Borders, investigates the movements of elephants through satellite collaring. Through the generous assistance of Wilderness Safaris guests Madeleine Delman Cohen and Jeffery Neu, we were able to collar two elephant cows and one bull in two areas critical to the northern Botswana elephant population. The first of these is the Linyanti Concession, formerly an area of exceptionally high elephant density in the dry season. The second was in the Mombo Concession, Moremi Game Reserve, where elephants are suspected of impacting on vegetation.
During the first month of monitoring, both elephants had modest movements, remaining close to permanent water sources. With rains beginning in November, both made considerable treks in pursuit of alternative resources. One of the cows followed the Savute Channel south-east, but returned to her original dry season home-range close to the Linyanti Marsh. However, the bull continued to move eastwards, 350km across the Mababe Depression towards Chinamba Hills in the southern Chobe National Park. Within this remote area elephants aggregate in their thousands around water-filled pans. During the three months we have been tracking their movements, the bull has ranged over a 7 000km2 area. An aerial flight was taken to track and attain a visual check of the bull; he was spotted amongst a breeding herd of approximately 40 elephants.
We will continue monitoring the collared elephants over the next four years to determine what influence water in the Savute Channel has on the seasonal home ranges, distribution and movements of elephants in the region. We will compare this data with the home ranges and seasonal movements of elephants when the Savute Channel was dry and with those collared along the once-dry Boteti River. This long-term spatial analysis will provide important information on the spatial ecology of elephants in these dynamic river systems.
January / February 2011
Up to date, the Trust has been involved with collaring four elephants, essentially as a result of funding by Wilderness Safaris guests. In total there are 18 elephant which have been collared in the initiative.
To summarise the movements of the three elephants mentioned in the previous monthly updates, we have found the following:
- Atticus – CH48 – collared in Linyanti in Oct 2010, currently spends all his time in Chobe NP near the Savute Marsh (Madeleine Delman-Cohen funded).
- Scout – CH46 – collared in Linyanti in Oct 2010, and has essentially shown fidelity to the concession area with slight movement in Chobe NP (Madeleine Delman-Cohen funded).
- Chloe – CH53 – collared at Mombo in Dec 2010, has not moved far, concentrating at the northern tip of Chief’s Island (Jeff Neu funded).