Population surveys of Nile crocodiles (Crocodylus niloticus) in the Murchison Falls National Park, Victoria Nile, Uganda
DOI:
https://doi.org/10.1515/eje-2017-0015Keywords:
Crocodiles, East Africa, natural history, management, conservationAbstract
1. A 12-month-long survey (April 2013 to March 2014) for Nile crocodiles (Crocodylus niloticus) was conducted along a section of the Victoria Nile/Ramsar site of Murchison Falls National Park, in order to update the historic information on crocodile populations in the area, locating nesting areas, determining seasonality patterns and habitat use, and assess the current abundance and the population size trends since the 1960s. The methods employed included visual encounter surveys, transect counts and opportunistic methods, by using boats.
2. In general, there were diurnal and seasonal fluctuations in the number of crocodile sightings. The crocodile sightings peaked between the months of June and August, with the highest mean number of sightings encountered on any single day being 67 (in July 2013), and the second peak was between January and March with the highest mean of 118 recorded in January 2014. The second peak also coincided with the crocodile breeding season. This clearly shows that the distribution of the sub-population sampled followed a climatic regime.
3. Crocodiles were observed most frequently in water (37%). Grassy banks, islands, river mouths and sandy banks constituted about 47% of the habitats utilised by the crocodile population. Although basking was the most frequent type of activity performed by crocodiles (50%) over the entire survey period, their key activities varied significantly from month to month. Nesting was very visible during the last quarter of the year and the first quarter of the New Year.
4. There was a clear decline of the abundance of crocodiles in this population between 1960s and nowadays. This declining trend was obvious also taking into account the various survey methodologies employed over the decades.
References
as a keystone species for aquatic ecosystem conservation in
South Africa: The case of the Olifants River. Aquatic Conservation:
Marine and Freshwater Ecosystems, 20, 489–493.
Baguma, R.K. (1996) Some ecological aspects of the Nile crocodile (Crocodylus
niloticus) in Murchison Falls National Park, Uganda. Master’s
Degree Programme Progress Report 11/96 to UWA, March
1996.
Behangana, M. (2014) Surveying crocodiles in the Victoria Nile/Ramsar
Site of Murchison Falls National Park. Reference: pr. 10001203.
Geo-Taxon Consult Ltd., Kampala, Uganda, pp. 67.
Bishop, J.M., Leslie, A.J., Bourquin, S.L. & O’Ryan, C. (2009) Reduced
effective population size in an overexploited population of the
Nile crocodile (Crocodylus niloticus). Biological Conservation,
142, 2335–2341.
Bonnet, X., Naulleau, G. & Shine, R. (1999) The dangers of leaving
home: dispersal and mortality in snakes. Biological Conservation,
89, 39–50.
Cott, H.B. (1961) Scientific results of an inquiry into the ecology and
economic status of the Nile crocodile (Crocodylus niloticus) in
Uganda and northern Rhodesia, Transactions of the Zoological
Society of London, 29, 211–358
Cott, H.B. (1968) The Status of the Nile crocodile below Murchison Falls.
Report to the Uganda National Parks, Kampala, Uganda. 9 pp.
Cott, H.B. (1969) Further observations on the status and biology of the
Nile crocodile below Murchison Falls. Report to Uganda National
Parks. Report to the Uganda National Parks, Kampala, Uganda.
12 pp.
Eniang, E.A., Akani, G.C., Vignoli, L., Luiselli, L. & Petrozzi, F. (2015) Sizerelated
habitat selection of a population of Nile monitors (Varanus
niloticus) from western Nigeria. African Journal of Ecology,
53, 246–248.
Filippi, E. & Luiselli, L. (2007) Non-random seasonal variation in the
structure of a Mediterranean snake community. Web Ecology,
7, 40–46.
Hekkala, E., Shirley, M.H., Amato, G., Austin, J.D., Charter, S., Thorbjarnarson,
J., Vliet, K.A., Houck, M.L., DeSalle, R. & Blum, M.J.
(2011) An ancient icon reveals new mysteries: mummy DNA
resurrects a cryptic species within the Nile crocodile. Molecular
Ecology, 20, 4199–4215.
Heyer, W.R., Donnely, M.A., Mc Diarmid, R.W., Hayek L.C. & Foster M.S.
(Eds.) (1994) Measuring and Monitoring Biological Diversity:
Standard Methods for Reptiles and Amphibians. Smithsonian
Institution Press, Washington.
Hovem, J.M., Tronstad, T.V., Karlsen, H.E. & Lokkeborg, S. (2012) Modeling
Propagation of Seismic Airgun Sounds and the Effects on
Fish Behavior. IEEE Journal of Oceanic Engineering, 37, 576–588.
Huchzermeyer, F.W. (2003) Crocodiles: biology, husbandry and disease.
CAB International, Wallingford.
Hurlbert, S.H. (1984) Pseudoreplication and the design of ecological
field experiments. Ecological Monographs, 54, 187–211.
Hutton, J.M. (1987) Growth and feeding ecology of the Nile crocodile
Crocodylus niloticus at Ngezi, Zimbabwe. Journal of Animal Ecology,
1987, 25–38.
Hutton, J.M. (1991) Crocodiles and their management in the Murchison
Falls National Park of Uganda. Agriconsulting/Uganda Institute
of Ecology, Kampala, Uganda.
Kofron, C.P. (1989) Nesting ecology of the Nile crocodile (Crocodylus
niloticus). African Journal of Ecology, 27, 335–341.
Krebs, C.J. (1966) Demographic changes in fluctuating populations of
Microtus californicus. Ecological Monographs, 36, 239–273.
Krebs, C.J. (1999) Ecological Methodology, 2nd ed. Harper and Row
Publ., New York, N.Y.
Lamprey R.H., Michelmore, F., Buhanga, F., Okecha, E., Omoding, J.,
Egunyu, J., Mukwaya, F.G., Behangana, M., Mafumbo, J. & Tiyoy,
L. (2000) Protected Area Systems Plan for Uganda, Vol. 4 Uganda
Wildlife Authority, Kampala.
Laurent, E.J. & Kingsbury, B.A. (2003) Habitat separation among three
species of water snakes in Northwestern Kentucky. Journal of
Herpetology, 37, 229–235.
Luiselli, L., Akani, G.C., Ebere, N., Angelici, F.M., Amori, G. & Politano, E.
(2012) Macro-habitat preferences by the African manatee and
crocodiles – ecological and conservation implications. Web Ecology,
12, 39–48.
Magnusson, W.E. (1985) Habitat selection, parasites and injuries in
Amazonian Crocodilians. Amazoniana, 9, 193–204.
Modha, M.L. (1967) The ecology of the Nile crocodile (Crocodylus niloticus
Laurenti) on Central Island, Lake Rudolf. African Journal
of Ecology, 5, 74–95.
Muhigwa, J.B. (1998) Diel activity and biotope choices of the Nile
Monitor Lizard in western Kenya. African Journal of Ecology, 36,
271–275.
Parker, I.S.C. (1969) Crocodile Distribution and Status in the Major Waters
of Western and Central Uganda. African Journal of Ecology,
8, 85–103.
Parker, I.S.C. & Watson, R.M. (1970) Crocodile Distribution and Status in
the Major Waters of Western and Central Uganda in 1969. East
African Wildlife Journal, S, 85–103.
Payne, J.F., C. Andrews & Fancey, L. (2008) Potential effects of seismic
energy on fish and shellfish: an update since 2003. Can. Sci. Advis.
Sec. Res. Doc.2008/060, Ottawa, Canada.
Pitman, C.R.S. (1952) Pigmy crocodiles in Uganda. The Uganda Journal
16(2), 119–124.
Plumptre, A.J., Ayebare, S., Mugabe, H., Kirunda, B., Kityo, R., Waswa,
S., Matovu, B., Sebuliba, S., Behangana, M., Sekisambu, R.,
Mulondo, P., Mudumba, T., Nsubuga, M., Isoke, S., Prinsloo, S.
& Nangendo, G. (2015) Biodiversity surveys of Murchison Falls
Protected Area. Wildlife Conservation Society, Kampala, Uganda,
pp. 26.
Thorbjarnarson, J. & Shirley, M.H. (2009a) Observations on Nile Crocodiles
(Crocodylus niloticus) and their Management in Murchison
Falls National Park. A Report to the Wildlife Conservation Society
and the Uganda Wildlife Authority, Kampala, Uganda.
Thorbjarnarson, J. & Shirley, M.H. (2009b) Population Assessment of
the Nile Crocodile (Crocodylus niloticus) in Kidepo Valley National
Park, northern Uganda. A Report to the Wildlife Conservation
Society and the Uganda Wildlife Authority, Kampala, Uganda.
Thorbjarnarson, J. & Shirley, M.H. (2011) Evaluation of the populations
of Nile Crocodile (Crocodylus niloticus) and Congo Dwarf Crocodile
(Osteolaemus osborni) in Queen Elizabeth and Lake Mburo
National Parks, Uganda. Wildlife Conservation Society, Kampala.
Wallace, K.M., & Leslie, A.J. (2008) Diet of the Nile crocodile (Crocodylus
niloticus) in the Okavango Delta, Botswana. Journal of Herpetology,
42, 361–368.
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Copyright (c) 2017 mathias Behangana, wilber lukwago, Daniele Dendi, Luca Luiselli, david ochanda
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