Cattle vs. hippopotamus: Dung in rivers of the Savannah

Date:
June 16, 2020
Source:
Forschungsverbund Berlin
Summary:
In many regions of the world, populations of large mammalian
herbivores have been displaced by cattle breeding, for example in
Kenya the hippos by large herds of cattle. This can change aquatic
ecosystems due to significant differences in the amount and type
of dung input. Researchers have therefore taken a closer look at
the dung of hippopotamus and cattle.



FULL STORY ==========================================================================
In many regions of the world, populations of large mammalian herbivores
have been displaced by cattle breeding, for example in Kenya the hippos
by large herds of cattle. This can change aquatic ecosystems due to
significant differences in the amount and type of dung input. Researchers
from the University of Eldoret in Kenya, the University of Innsbruck and
the Leibniz- Institute of Freshwater Ecology and Inland Fisheries (IGB)
have therefore taken a closer look at the dung of hippopotamus and cattle.


========================================================================== Animal dung can pollute water bodies with nutrients and impact water
quality and the ecological functions of water bodies. For many aquatic ecosystems, however, the input of organic matter from the surrounding
land is part of the natural matter cycling. In temperate latitudes,
it is the leaf fall that brings nutrients into water bodies. In the
rivers of the African savannah, it is the hippos with their dung. The increasing displacement of hippopotami by herds of cattle is changing
the nutrient inputs into water bodies.

Professor Gabriel Singer, Dr. Frank O. Masese and their team investigated
the effects of nutrient and carbon inputs from dung on aquatic ecosystems
in experiments. The researchers also developed a mathematical model
to compare dung inputs from cattle and hippos into the Mara River in
Kenya. According to the mathematical simulation, despite lower manure introduction by the individual cattle compared to a hippopotamus, the
large number of cattle gives this animal group overwhelming influence.

Cattle dung is more nutritious and stimulates the growth of plants,
bacteria and algae With cattle dung, higher amounts of nutrients such as nitrogen, phosphorus and dissolved organic carbon enter the Mara River. In
the experiments, the researchers were able to show that, as a result,
more plant biomass is formed with cattle dung. The biomass of bacteria
and algae was also higher than with hippopotamus dung. This can change
food webs in the river.

"Just the exchange of an animal species that lives on the edge of the
river changes the ecological status of the river. Our results show the
high species- specific importance of the various large herbivores; they
also show how changes in land use or the composition of the species lead
to unintended consequences that are not initially the focus of management measures, but which must always be taken into account. Especially with
such crucial ecosystems as the waters of the savannah," Gabriel Singer
explains the significance of the investigation.


========================================================================== Story Source: Materials provided by Forschungsverbund_Berlin. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Frank O. Masese, Mary J. Kiplagat, Clara Romero Gonza'lez-Quijano,
Amanda
L. Subalusky, Christopher L. Dutton, David M. Post, Gabriel
A. Singer.

Hippopotamus are distinct from domestic livestock in their resource
subsidies to and effects on aquatic ecosystems. Proceedings of the
Royal Society B: Biological Sciences, 2020; 287 (1926): 20193000
DOI: 10.1098/ rspb.2019.3000 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200616135746.htm

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