Why the African clawless otter is tenfold brainier than the African striped weasel

Everyone knows that the human species is brainier than various other kinds of primates. However, what is not widely realised is how much brainier some carnivores are than others.

Figures for the braininess of 30 species of carnivores living near the southern tip of Africa can be found in https://www.tandfonline.com/doi/pdf/10.1080/02541858.1984.11447899. This information has been available for nearly three decades, but it is worth repeating in plain language, because the findings may still surprise naturalists.

Among those studied by measuring brain volumes relative to body mass, the species closest to average (i.e. with an encephalisation quotient of about 1.0) are the Cape fox (Vulpes chama, https://en.wikipedia.org/wiki/Cape_fox#/media/File:Vulpes_chama_(Etosha).jpg), the aardwolf (Proteles cristatus, https://en.wikipedia.org/wiki/Aardwolf#/media/File:Proteles_cristatus1.jpg), the marsh mongoose (Atilax paludinosus, http://portugal.inaturalist.org/taxa/41919-Atilax-paludinosus) and a range of felids weighing from less than 5 kg to more than 100 kg.

Note that most wild cats are about as brainy as expected for the average mammal, including the average carnivore.

However, three species are about twice as brainy (encephalisation quotient about 2.0) as this standard would predict. These are the African clawless otter (Aonyx capensis, https://upload.wikimedia.org/wikipedia/commons/6/69/Aonyx_capensis%2C_male%2C_Shamvura.jpg), the honey badger (Mellivora capensis, https://en.wikipedia.org/wiki/Honey_badger#/media/File:Mellivora_capensis_in_Howletts_Wild_Animal_Park.jpg) and the African hunting dog (Lycaon pictus, https://upload.wikimedia.org/wikipedia/commons/b/ba/African_wild_dog_%28Lycaon_pictus_pictus%29.jpg). This kind of otter has primate-like dexterity; the honey badger is smart enough to use tools even though it is not dexterous; and the African hunting dog uses extreme teamwork to compete with, and evade punishment from, felids and hyenas with far more brawn.

Also on the brainy side are the brown hyena (Parahyaena brunnea,

https://upload.wikimedia.org/wikipedia/commons/5/50/Brown_Hyena_%28Hyaena_brunnea%29_leaving_waterhole_..._%2850915531592%29.jpg),

caracal (Caracal caracal, https://upload.wikimedia.org/wikipedia/commons/1/12/Caracal_on_the_road%2C_early_morning_in_Kgalagadi_%2836173878220%29.jpg)

, black-backed jackal (Lupulella mesomelas, https://en.wikipedia.org/wiki/Black-backed_jackal#/media/File:Black-backed_jackal_(Canis_mesomelas_mesomelas)_2.jpg) and spotted-necked otter (Hydrictis maculicollis, https://en.wikipedia.org/wiki/Spotted-necked_otter#/media/File:Spotted-necked_otter_1.jpg). These share encephalisation quotients of about 1.3, despite belonging to four different families.

Somewhat below average in braininess is the diminutive, shy black-footed cat (Felis nigripes, https://en.wikipedia.org/wiki/Black-footed_cat#/media/File:Zoo_Wuppertal_Schwarzfusskatze.jpg). This has a similar encephalisation quotient (about 0.7) to the like-size Egyptian mongoose (Herpestes ichneumon, https://www.naturepl.com/stock-photo-egyptian-mongoose-herpestes-ichneumon-captive-at-friguia-park-tunisia-image01507979.html).

Surprisingly limited in braininess are the genets and most mongooses, including the meerkat (Suricata suricatta, https://upload.wikimedia.org/wikipedia/commons/9/9a/Meerkat_%28Suricata_suricatta%29_Tswalu.jpg). Given the smart, social behaviour and anthropomorphic appeal of this species, it is hard to believe that its encephalisation quotient is only 0.3. Equally unexpected is that the common dwarf mongoose (Helogale parvula, https://upload.wikimedia.org/wikipedia/commons/0/05/Dwarf_Mongoose_%28Helogale_parvula%29_%286002158282%29.jpg), another social species, has an encephalisation quotient of less than 0.2, tenfold less than that of the most social canid, the African hunting dog.

Least brainy is the African striped weasel (Poecilogale albinucha, https://en.wikipedia.org/wiki/African_striped_weasel#/media/File:Whitenapedweasellg2.jpg), which means that the family Mustelidae spans the full range of values found in this study. The African striped weasel (0.16) and the striped polecat (Ictonyx striatus, encephalisation quotient 0.3, https://www.agefotostock.com/age/en/details-photo/africa-namibia-private-reserve-striped-polecat-or-african-polecat-ictonyx-striatus-captive/D88-3525771) both have warning colouration and rely on noxious substances, not intelligence, to avoid victimisation by other carnivores.

Posted on 25 de julho de 2021, 04:28 AM by milewski