Sundry notes on the natural history of the common hippopotamus (Hippopotamus amphibius) in the late 'fifties in Maputaland, by Kenneth L. Tinley

@christiaan_viljoen @tonyrebelo @jeremygilmore @davidbygott @dejong @paradoxornithidae @botswanabugs @nyoni-pete @wynand_uys @variani18

Also see https://www.inaturalist.org/journal/milewski/82576-notes-on-the-common-hippopotamus-hippopotamus-amphibius-from-haller-park-mombasa-kenya#

Kenneth L. Tinley, now 88 years old (https://gorongosa.org/montane-to-mangrove/ and https://www.perplexity.ai/search/when-was-ken-l-tinley-the-ecol-LLDEAfWMTV2UFV3vAeOA0A and https://gorongosa.org/montane-to-mangrove/) was, during the 'seventies, perhaps the best-known wildlife ecologist in South Africa.

Tidying up my library today, I came across an obscure article he published at the start of his tertiary education.

Tinley, although a mere first-year student at the University of Natal at the time, wrote:
Tinley K L (1961) 'Hippos' Nucleon 3: 39-42 (journal of the University of Natal Science Society).

The information in this always-obscure, now-forgotten, article remains of interest today, because it was based on Tinley's field experience as a game ranger in what is now northern KwaZulu-Natal (https://en.wikipedia.org/wiki/Maputaland) during the several years after he completed his secondary education (high school).

In this Post, I quote selectively from Tinley (1961) for the sake of posterity. I have chosen these quotes on the basis that his interpretations remain relevant to this day, despite many detailed field-studies of the common hippopotamus by other authors subsequently, in various parts of Africa.

"If a sleeping herd is disturbed, one or more of the animals will yawn widely, often rearing up and falling backwards or sideways into the water. From one animal yawning, most of the other members of the herd follow suit, leaving the observer (often yawning himself) impressed with the large dentition of the older members. Yawning is especially noticeable in the late afternoon just before the herd moves out onto the land to graze."

"Although grass makes up the bulk of their diet, some aquatic plants, including a few sedge species and the tubers of water lilies (Nymphaea spp.) are also eaten. It is not known whether the hippo obtains these tubers by grubbing them out with the two forward projecting incisors, or whether it paws them out with its front feet. They usually return to the surface to chew the gathered mouthful of tubers."

https://www.inaturalist.org/observations?place_id=13313&taxon_id=51122&view=species and https://www.inaturalist.org/observations?place_id=13313&taxon_id=321501 and https://www.inaturalist.org/observations?place_id=13313&taxon_id=165755

"Both large and very small grasses are eaten; they can often be observed grazing the flat-tufted or creeping lawn grasses which grow in abundance at the margins of their aquatic habitat. Grass blades as small as 4 cm are readily cropped, and with some of the larger broad leaved varieties, only the tips are taken."

https://www.shutterstock.com/video/clip-1044603814-close-hippo-grazing and https://www.shutterstock.com/video/clip-3476771257-close-head-wild-afrcian-hippopotamus-grazing-grasslands and https://www.shutterstock.com/video/clip-3476782029-close-head-wild-afrcian-hippopotamus-grazing-grasslands and https://www.shutterstock.com/video/clip-3476773255-full-body-close-hippopotamus-grazing-great-egret and https://www.shutterstock.com/video/clip-3475059649-beautiful-wild-hippo-hippopotamus-amphibius-grazing-chobe

"...there is a calloused ridge on the upper lip, slightly serrated in parts. When grazing, the lower lip is closed against the calloused pad of the upper, and the head nodded downwards, thus nipping off the tips of the short grasses or stems of the larger types; the efficiency of this method is facilitated by the large lips enclosing the teeth. Presumably the tongue is used to convey the food back into the mouth, as it is frequently seen projecting just beyond the lips while the animal is chewing."

https://www.pond5.com/stock-footage/item/61258033-close-hippos-open-mouth-and-teeth and https://es.123rf.com/photo_87765253_close-up-image-of-hippo-s-mouth.html

"Fighting [between rival males] usually begins in the water, but often during the course of the fight they will move out on to the land, usually due to the attempt of one of the bulls to retreat from his adversary, who will usually give chase. As often as not the bulls fight till [sic] one is killed, but if the loser is a young bull it may hurriedly retire to some remote haunt to recuperate till [sic] strong enough to tackle a herd bull again. At the scene of the battle large areas will be found flattened and torn up, with blood spattered everywhere, to chest height against the trees and bushes. Most fights occur at night and only the preliminary stages of these battles have been witnessed. The two bulls face one another uttering a deep low rumbling bellow, and every now and then raise their posterior end and patter the water loudly by succeasive sideways movements of the short flattened tail. (This tail movement is usually but not always made when defaecating.) When attacking, the mouth is kept wide open and powerful forward upward thrusts of the lower jaw are executed bringing into play the two large forward projecting tusk-like incisors. Deaths in fighting usually occur as a result of the smashing of the ribs just behind the scapular [sic] from upward lunging blows of the incisors and lower Jaws. The sharp curved canines inflict enormous gaping wounds up to a foot in diameter, or long deep gashes. Throughout the fight there is a tremendous uproar due to the bellowing, roaring and screaming of the opponents."

"The cow hippo leaves the water...and gives birth in sheltered bush not far from the water. If the calf is a female it is soon brought back to the herd, but if a male is born the mother and calf remain in seclusion or move further away from the herd. For if mature bulls...find bull calves they kill them immediately. This seemingly paradoxical 'survival factor' probably operates to ensure that not too many bulls come to maturity, thus preventing too much competition...If crocodiles have not consumed the remains, dead butchered remains of small bull calves may often be found, or careful observation will enable the observer to locate the mother and calf hiding in some unfrequented sector."

"When lying down the animal lowers the front half of the body first in the same manner as the cow, but in getting up they raise the front first in the same manner as the horse...Hippo are able to swim on the surface of the water...When swimming at speed in deep water the hind limbs are trailed out immobile behind them, and the swimming is done by 'walking-paddling motions' of the powerful fore limbs...Hippo calves often stand on their mother's backs when the latter are resting. In these situations they are persistently bothered by biting flies (Tabanus spp....) which settle, generally on the head, to suck blood. The bite irritates the hippo, but by moving their ears in a peculiar quick circular movement they throw up a spray of water which repels the insects...In winter hippo often lie out asleep on the shore, probably because the water is too cold, the solar radiation less than in summer, and because there are no biting flies."

https://www.inaturalist.org/observations?place_id=13313&taxon_id=49704&view=species and https://www.inaturalist.org/observations?place_id=13313&taxon_id=47821&view=species

MY COMMENTARY

I am surprised that Tinley experienced the yawning of the common hippopotamus as personally contagious. My reason is that this is a 'fang-baring' expression,

• analogous to that in baboons (Papio spp., https://www.sciencephoto.com/media/87037/view/hamadryas-baboon-papio-hamadryas- and https://www.alamy.com/hamadryas-baboon-papio-hamadryas-male-with-open-mouth-defensive-posture-image387705595.html and https://www.gettyimages.com.au/detail/photo/tusk-royalty-free-image/1149804234?phrase=baboon+fangs&adppopup=true), and
• signifying warning, not relaxation.

The difference in 'fang-baring' between baboons and the common hippopotamus is that in the former it is restricted to adult males, whereas in the latter it is performed by both sexes and juveniles as well as adults.

The diet of the common hippopotamus in Maputaland has subsequently been studied in great detail (https://journals.co.za/doi/pdf/10.10520/AJA03794369_3154).

The possibility that the common hippopotamus excavates tubers with its lower incisors is important w.r.t. the overall foraging niche of the species. It is remarkable that Tinley's suggestion has not been confirmed, or proven incorrect, in the elapsed 65 years (https://www.perplexity.ai/search/has-hippopotamjs-amphibius-bee-0G7uksfIS0C3lI1P5c0Mmw).

A related point:
I have not seen confirmation that males use the lower incisors to smash the rib-cage of rivals.

The question of the various functions of the lower incisors of the common hippopotamus remains important, because

• these ever-growing teeth peculiar and not particularly sexually dimorphic, and
• geophagy (https://en.wikipedia.org/wiki/Geophagia) is nutritionally important in large herbivores.

Laws (1968, https://www.semanticscholar.org/paper/DENTITION-AND-AGEING-OF-THE-HIPPOPOTAMUS-Laws/fb59f56b17cd2d5afbb472621de5b643617e7309 and https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2028.1968.tb00899.x and https://www.researchgate.net/publication/229967272_Dentition_and_ageing_of_the_hippo) states: "canines and incisors...the former being used exclusively for fighting and the latter for digging and possibly for fighting. The wear pattern suggests that the incisors are used for digging, and observations at localities where there are natural mineral deposits have shown that hippopotamus do use the incisors for mining earth in these places."

The following show the protruding tongue:
https://www.gettyimages.in/detail/photo/hippopotamus-sticking-tongue-out-royalty-free-image/522653264?adppopup=true
https://www.gettyimages.in/detail/photo/hippopotamus-with-tongue-out-royalty-free-image/154566768?adppopup=true.

Infanticide by mature males has been confirmed since Tinley's time (https://africageographic.com/stories/graphic-video-hippo-commits-infanticide/ and https://www.facebook.com/WildlifePhotographerOfTheYear/photos/warning-you-may-find-this-image-distressing-in-this-dramatic-and-disturbing-imag/2385639291490106/ and https://www.facebook.com/WildlifePhotographerOfTheYear/posts/infanticide-among-hippos-is-rare-but-not-unknownwpyalumni-adrian-hirschi-capture/601852557964472/ and https://www.facebook.com/Jackalexpeditionsptyltd/posts/infanticide-among-hippos-is-rare-but-not-unknownwpyalumni-adrian-hirschi-capture/1393395267835118/), e.g. in the reintroduced population at Rondevlei near Cape Town (https://en.wikipedia.org/wiki/Rondevlei_Nature_Reserve and https://allafrica.com/stories/200312120631.html and https://www.iol.co.za/technology/hip-hipporay-for-brutuss-new-vlei-nymphs-118686 and https://allafrica.com/stories/200312160576.html).

However, the routine targeting of male infants remains remarkable and paradoxical.

I have before me a press-clipping from S A Independent newspaper (which is defunct), dated 10 August 1999 (25 years ago). It is titled "Brutus the killer hippo".

It reads "Brutus has killed nine of his 15 offspring in the past nine years. And it appears he's responsible for the recent death of his partner, Portia, and her two-week old baby. Brutus, the only male hippo at Rondevlei Bird Sanctuary, was imported from KwaZulu-Natal many years ago...Dean Ferreira (https://za.linkedin.com/in/dean-ferreira-8191813a), in charge of nature conservation for the South Peninsula municipality, says...only three of 15 hippos born at Rondevlei over the years have survived. Two were sold to other reserves, and there is a (presumably somewhat nervous) 18-month-old still at Rondevlei. Nine have been gouged to death. Said Ferreira: 'We didn't even know a new calf had been born until we found it dead with the adult female last week. There were teeth marks on the adult. We think that the baby died because its mother had died.' "

Tinley went on to publish, in 1964, a peer-reviewed paper on tabanid flies and their relationships to the common hippopotamus:
https://resjournals.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-3032.1964.tb00789.x and https://www.researchgate.net/publication/230313480_Some_observations_on_certain_tabanid_flies_in_North-Eastern_Zululand_Diptera_Tabanidae

Publicado el 15 de agosto de 2024 por milewski