Editing Hippopotamus (section)

===Interspecies interactions===
[[File:Kruger-Park-Hippo-And-Crocodile.jpg|thumb|right|A hippopotamus and Nile crocodile side by side in Kruger National Park]]
Hippos coexist alongside a variety of large predators in their habitats. [[Nile crocodile]]s, [[lion]]s, and [[spotted hyena]]s are known to prey on young hippos.<ref name=estes/> Beyond these, adult hippos are not usually preyed upon by other animals due to their aggression and size. Cases where large lion prides have successfully preyed on adult hippos have been reported, but it is generally rare.<ref>{{cite book|last = Hunter|first = Luke|title = Carnivores of the World|publisher = [[Princeton University Press]]|year = 2011|isbn = 978-0-691-15228-8}}</ref> Lions occasionally prey on adults at [[Gorongosa National Park]] and calves are sometimes taken at Virunga.<ref>{{Cite book | last= Schaller |first= George B. |year= 1972 |title= The Serengeti lion: A study of predator–prey relations|publisher= University of Chicago Press|pages=208–209|isbn = 978-0-226-73639-6 }}</ref> [[Crocodile]]s are frequent targets of hippo aggression, probably because they often inhabit the same [[riparian]] habitats; crocodiles may be either aggressively displaced or killed by hippos.<ref>{{cite book|last1 = Ross|first1 = Charles A.|last2 = Garnett|first2 = Stephen|title = Crocodiles and Alligators|publisher = Checkmark Books|year = 1989|isbn = 978-0-8160-2174-1}}</ref> Although they will avoid crocodiles larger than {{cvt|3.5|m}}.<ref name="Kofron 1993">{{cite journal |last=Kofron |first=Christopher |title= Behavior of Nile Crocodiles in a Seasonal River in Zimbabwe |journal= American Society of Ichthyologists and Herpetologists |date=May 3, 1993 |volume=1993 |issue=2 |pages=463-469 |jstor= 1447146}}</ref> In turn, very large Nile crocodiles have been observed preying occasionally on calves, "half-grown" hippos, and possibly also adult female hippos. Groups of crocodiles have also been observed finishing off still-living male hippos that were previously injured in mating battles with other males.<ref name="Cott">{{cite journal|author=Cott, H. B. |title=Scientific results of an inquiry into the ecology and economic status of the Nile crocodile (''Crocodilus niloticus'') in Uganda and Northern Rhodesia|journal=The Transactions of the Zoological Society of London|volume=29|issue=4|pages=211–356|doi=10.1111/j.1096-3642.1961.tb00220.x|year=2010}}</ref><ref name="Guggisberg">{{cite book | author = Guggisberg, C. A. W. | title = Crocodiles: Their Natural History, Folklore, and Conservation| year = 1972 | isbn = 978-0-7153-5272-4 | page = 195| publisher = David & Charles}}</ref>

Hippos occasionally visit [[cleaning stations]] in order to be cleaned of parasites by certain species of fishes. They signal their readiness for this service by opening their mouths wide. This is an example of [[Mutualism (biology)|mutualism]], in which the hippo benefits from the cleaning while the fish receive food.<ref>{{cite book|author1 =Balcombe, Jonathan|year=2006|title=Pleasurable Kingdom: Animals and the Nature of Feeling Good|url =https://archive.org/details/pleasurablekingd00balc_653|url-access =limited|publisher=Palgrave Macmillan|pages=[https://archive.org/details/pleasurablekingd00balc_653/page/n140 132]–133|isbn=978-1-4039-8602-3}}</ref> Hippo defecation creates [[allochthonous]] deposits of organic matter along the river beds. These deposits have an unclear ecological function.<ref name="Grey">{{Cite journal|title = Using Stable Isotope Analyses To Identify Allochthonous Inputs to Lake Naivasha Mediated Via the Hippopotamus Gut| author = Grey, J.| author2 = Harper, D. M.|journal = Isotopes in Environmental Health Studies|volume = 38|issue = 4|year = 2002|pages = 245–250|doi = 10.1080/10256010208033269| pmid = 12725427| bibcode = 2002IEHS...38..245G| s2cid = 216152807}}</ref> A 2015 study concluded hippo dung provides nutrients from terrestrial material for fish and aquatic invertebrates,<ref>{{cite journal|author=McCauley, D. J.|year=2015|title=Carbon stable isotopes suggest that hippopotamus-vectored nutrients subsidize aquatic consumers in an East African river|journal=Ecosphere|volume=6|issue=4|pages=1–11|doi=10.1890/ES14-00514.1|display-authors=etal|doi-access=free}}</ref> while a 2018 study found that their dung can be toxic to aquatic life in large quantities, due to absorption of dissolved oxygen in water bodies.<ref>{{cite journal|author1=Dutton, C. L. |author2=Subalusky, A. L. |author3=Hamilton, S. K. |author4=Rosi, E. J. |author5=Post, D. M. |year=2018|title=Organic matter loading by hippopotami causes subsidy overload resulting in downstream hypoxia and fish kills|journal=Nature Communications|volume=9|issue=1951|page=1951 |doi=10.1038/s41467-018-04391-6|pmid=29769538 |pmc=5956076|bibcode=2018NatCo...9.1951D }}</ref><ref>{{cite web |url=https://www.theatlantic.com/science/archive/2018/05/hippos-poop-so-much-that-sometimes-all-the-fish-die/560486/ |title=Hippos Poop So Much That Sometimes All the Fish Die |last=Yong |first=Ed |work=The Atlantic |date=16 May 2018 |access-date=23 June 2021 }}</ref>

The parasitic [[monogenea]]n [[flatworm]]'' Oculotrema hippopotami'' infests hippopotamus eyes, mainly the nictitating membrane. It is the only monogenean species (which normally live on fish) documented to live on a mammal.<ref>{{cite journal|author1=Rubtsova, N. Y.|author2=Heckmann, R. A.|author3=Smit, W. J.|author4=Luus-Powell, W. J.|author5=Halajian, A.|author6=Roux, F.|year=2018|title=Morphological studies of developmental stages of ''Oculotrema hippopotami'' (Monogenea: Polystomatidae) infecting the eye of ''Hippopotamus amphibius'' (Mammalia: Hippopotamidae) ssing SEM and EDXA with notes on histopathology|journal=The Korean Journal of Parasitology|volume=56|issue=5|pages=463–475|doi=10.3347/kjp.2018.56.5.463|pmid=30419732 |pmc=6243182 |s2cid=53289954 }}</ref>