Termite-eating foxes in Africa and South America are surprisingly different

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The bat-eared fox (Otocyon megalotis, https://www.inaturalist.org/taxa/42095-Otocyon-megalotis) and the hoary fox (Lycalopex vetulus, https://www.inaturalist.org/taxa/516127-Lycalopex-vetulus) are both small canids.

Both species have been reviewed in the series Mammalian Species:
https://academic.oup.com/mspecies/article/doi/10.2307/3504550/2600516?login=false
https://www.jstor.org/stable/mammalianspecies.41.847.1

Both species semi-specialise on insectivorous diets (https://www.researchgate.net/publication/47296021_Diet_of_bat-eared_foxes_Otocyon_megalotis_in_the_Karoo and https://animaldiversity.org/accounts/Lycalopex_vetulus/).

The bat-eared fox occurs in Africa, whereas the hoary fox occurs in South America.
 
This may sound like a case of evolutionary convergence. However, in reality the differences are more instructive than the similarities.
 
The bat-eared fox is a classic example of the arid/eutrophic pattern of distribution (http://upload.wikimedia.org/wikipedia/commons/7/73/Bat-eared_Fox_area.png and https://www.researchgate.net/publication/229892875_Rainfall_soil_nutrient_status_and_biomass_of_large_African_savanna_mammals and https://www.researchgate.net/publication/222818600_The_evolution_of_arid_ecosystems_in_Eastern_Africa and https://link.springer.com/chapter/10.1007/978-3-642-68786-0_6?noAccess=true).

By contrast, the hoary fox exemplifies a wet/dystrophic pattern. It is restricted to the cerrado (https://en.wikipedia.org/wiki/Cerrado) of Brazil (http://upload.wikimedia.org/wikipedia/commons/2/22/Hoary_Fox_area.png and https://www.shutterstock.com/image-photo/hoary-fox-595359773https://www.agefotostock.com/age/en/details-photo/hoary-fox-lycalopex-vetulus-walking-on-sand-path-pantanal-mato-grosso-do-sul-brazil/IBK-4544175).

In African savanna comparable with the cerrado in climate and soils, the bat-eared fox is absent. Furthermore, there is no canid specialising on insects - although some mongooses do so - in that biome in Africa.
 
The bat-eared fox has extremely large ear pinnae (https://www.alamy.com/stock-photo-bat-eared-fox-otocyon-megalotis-kgalagadi-transfrontier-park-south-74736952.html) and extremely reduced teeth. This makes it the most aberrant of African canids.

The bat-eared fox is also odd in having a facial mask (https://www.alamy.com/stock-photo-bat-eared-fox-otocyon-megalotis-adult-on-dry-grass-masai-mara-park-111520882.html and https://www.alamy.com/stock-photo-bat-eared-fox-otocyon-megalotis-savute-north-west-district-botswana-74749144.html and https://fineartamerica.com/featured/1-bat-eared-fox-tony-camachoscience-photo-library.html and https://animals.sandiegozoo.org/animals/bat-eared-fox and https://wholeeartheducation.com/bat-eared-fox/ and https://www.alamy.com/bat-eared-fox-otocyon-megalotis-serengeti-tanzania-africa-image403319601.html and https://www.alamy.com/stock-photo-bat-eared-fox-otocyon-megalotis-young-bat-eared-foxes-in-savannah-47937640.html and https://www.alamy.com/bat-eared-fox-otocyon-megalotis-serengeti-national-park-tanzania-east-image63682430.html).

By contrast, the hoary fox could hardly be more generalised in body form. It is a near-perfect example of a small but otherwise average-looking canid.

https://www.superstock.com/asset/hoary-fox-dusicyon-vetulus-brazil/4141-1864
https://www.zoochat.com/community/media/hoary-fox-lycalopex-vetulus.230872/
https://www.alamy.com/hoary-fox-lycalopex-vetulus-in-dense-bushes-pantanal-mato-grosso-do-image155954011.html
 
The diets of the two species, while categorically similar, actually differ in important ways.

The bat-eared fox eats termites and beetles as staples. It tends to depend on Hodotermes (https://www.inaturalist.org/taxa/558312-Hodotermes-mossambicus). This is a termite with no ecological counterpart in South America - least of all in the cerrado.

The hoary fox instead eats the termite Syntermes (https://www.inaturalist.org/observations?place_id=any&taxon_id=548075&view=species) as a staple.

The bat-eared fox has the most reduced dentition found in any canid, in the sense that the teeth are small but numerous (https://www.mindenpictures.com/stock-photo-bat-eared-fox-otocyon-megalotis-skull-adult-more-teeth-than-any-other-naturephotography-image80094385.html and http://skullbase.info/skulls/mammals/bat-eared_fox.php and http://digimorph.org/specimens/Otocyon_megalotis/female/ and http://www.skullsite.co.uk/Batfox/batfox_lat.htm).

Compare this with the hoary fox: https://commons.wikimedia.org/wiki/File:Lycalopex_vetulus_skull_mod_after_Mivart_%281890%29.jpg.
 
BAT-EARED FOX
  
The bat-eared fox has deeply penetrated the Western Cape of South Africa: https://cederbergcaracalproject.files.wordpress.com/2012/02/otocyon2.jpg and https://en.wikipedia.org/wiki/Cederberg.

This emphasises that the bat-eared fox is capable of surviving even in a mediterranean-type climate, where Hodotermes is replaced by Microhodotermes.

The bat-eared fox also penetrates the ecosystems richest in large mammals, e.g. the Serengeti.
 
https://en.wikifur.com/wiki/Bat-eared_fox
http://i17.photobucket.com/albums/b53/Rawine81/220L-Bat-Eared-Fox.jpg 
https://www.alamy.com/stock-photo-bat-eared-fox-otocyon-megalotis-28869975.html
https://www.alamy.com/stock-photo-bat-eared-fox-otocyon-megalotis-adult-on-dry-grass-masai-mara-park-111520881.html
http://upload.wikimedia.org/wikipedia/commons/f/ff/Bat_eared_fox_Kenya_crop.jpg
https://en.wikipedia.org/wiki/Bat-eared_fox#/media/File:Otocyon_megalotis_-_Etosha_2014.jpg
https://www.alamy.com/bat-eared-fox-otocyon-megalotis-standing-in-savanna-south-africa-kgalagadi-transfrontier-national-park-image255390916.html
 
The tail can be raised and laterally flattened, to display the contrast between the dark dorsal surface and pale sides of the tail. This should be interpreted in conjunction with the facial mask.
 
https://doupienaar.files.wordpress.com/2011/11/bat-eared-fox-on-the-trot_0wm1.jpg
 
The following show how the bat-eared fox uses its tail as a shield and distraction in flight from predators.
 
https://www.reddit.com/r/natureismetal/comments/ab7h1y/cheetah_chasing_a_bateared_fox/
https://www.agefotostock.com/age/en/details-photo/two-cheetahs-acinonyx-jubatus-chasing-bat-eared-fox-otocyon-megalotis-maasai-mara-national-reserve-kenya/AAM-AAES73153
https://www.grantatkinson.com/wp-content/uploads/2015/06/HelenaAtkinson_Kalahari-64051.jpg

This suggests that the bat-eared fox possesses a caudal flag, whereas the hoary fox does not.

However, the caudal flag of the bat-eared fox is not activated during normal running (https://www.alamy.com/stock-photo-bat-eared-fox-running-74411933.html?imageid=C8630CE7-C721-40C9-8825-53531842383A&p=226538&pn=1&searchId=9dfad990ce03d5201da9157a49b9c5ce&searchtype=0 and https://www.alamy.com/stock-photo-bat-eared-fox-long-eared-fox-big-eared-fox-otocyon-megalotis-virgatus-31879524.html?imageid=A3BC9750-14D0-4C8D-A483-862F61A89DDE&p=86574&pn=1&searchId=8a549727400865991a78de52aba425ae&searchtype=0).

HOARY FOX
 
It is difficult to imagine a more generalised-looking (primitive?) canid than the hoary fox. The species looks nondescript, despite the emphasis on termites in its diet.
 
https://twitter.com/factualanimal/status/897623546838515713
https://www.inaturalist.org/observations/103417435
http://www.canids.org/app/images/canids/hoary-fox/hoary.jpg
https://www.inaturalist.org/observations/117669510
https://www.inaturalist.org/observations/111990990

I would describe the hoary fox as resembling a small jackal or miniature coyote, rather than true foxes (Vulpes, https://en.wikipedia.org/wiki/Vulpes and https://www.worldatlas.com/articles/the-six-species-of-south-american-fox.html).

http://creagrus.home.montereybay.com/trip-Brazil10/FoxHoa-24Jul10Emas_1044r.jpg
https://www.inaturalist.org/observations/97804152
https://www.inaturalist.org/observations/90300970
https://www.inaturalist.org/observations/55551331
https://kidadl.com/facts/animals/hoary-fox-facts
https://www.researchgate.net/figure/Female-hoary-fox-Lycalopex-vetulus-specimen-Photo-source_fig1_330201202

The long tail of the hoary fox has a dark tip, similar to the pattern seen in many canids. However, the tail - like the face and ear pinnae - is otherwise unremarkable.
 
https://www.flickr.com/photos/artour_a/48986093627
https://www.shutterstock.com/image-photo/hoary-fox-595359773
https://www.agefotostock.com/age/en/details-photo/hoary-fox-lycalopex-vetulus-walking-on-sand-path-pantanal-mato-grosso-do-sul-brazil/IBK-4544175 
http://i.ytimg.com/vi/rLA3yVgSwxk/maxresdefault.jpg

DISCUSSION

The caudal flag, and perhaps in part the facial mask, of the bat-eared fox can be explained by the intense regime of predation to which it is adapted.

However, the extreme size of the ear pinnae has yet to be fully explained.

The ears may be specialised for locating rustling insects, including the buried larvae of dung beetles. However, the fact that the ear pinnae are not correspondingly enlarged in the hoary fox suggests a thermoregulatory function in the semi-deserts inhabited by the bat-eared fox.

Posted on 14 de julho de 2022, 06:14 PM by milewski