Kobus kob kob as the West and Central African counterpart for the common impala (Aepyceros melampus), part 2

...continued from https://www.inaturalist.org/journal/milewski/90862-kobus-kob-kob-as-the-west-and-central-african-counterpart-for-the-common-impala-aepyceros-melampus-part-1#

GAITS AND POSTURES

Walking

Reduncin bovids usually walk with a gait that I call a semi cross-walk, suited to slippery ground, wading, and (in the case of Redunca) cover-dependence and crypsis.

A semi cross-walk is sometimes evident in K. k. kob (https://www.inaturalist.org/observations/6441928 and https://www.inaturalist.org/observations/103751919 and https://www.inaturalist.org/observations/49540044 and https://www.inaturalist.org/observations/6576868 and, with excellent clarity, https://www.inaturalist.org/observations/6443567).

Furthermore, K. k. kob sometimes cross-walks while wading (https://www.inaturalist.org/observations/4455437).

However, K. k. kob usually walks with a gait that I call an amble (https://www.flickr.com/photos/24544467@N02/14116742194 and https://www.inaturalist.org/observations/6576874 and https://www.inaturalist.org/observations/9619322 and https://www.inaturalist.org/observations/29326373 and https://www.inaturalist.org/observations/90271797 and https://www.inaturalist.org/observations/103751934 and https://www.inaturalist.org/observations/103751852 and https://www.inaturalist.org/observations/103751803 and https://www.inaturalist.org/observations/6442753 and https://www.inaturalist.org/observations/5221625 and https://www.inaturalist.org/observations/150407398).

In this way it is convergent with A. melampus, which ambles (https://www.alamy.com/impala-or-rooibok-aepyceros-melampus-melampus-mosi-oa-tunya-national-park-zambia-africa-unesco-world-heritage-site-image570163886.html?imageid=01351974-461E-485E-9325-8E9B7BF951DD&p=781377&pn=5&searchId=e922776e8d1e36d28092ccbdc8ef1ed9&searchtype=0).

The diagnostic criterion is as follows. Please focus on the hind hoof.

• in a semi cross-walk, the hind leaves the ground before the opposite fore touches the ground, whereas
• in an amble, the hind leaves the ground only once the opposite fore has touched the ground.

The following, showing a semi cross-walk in A. melampus, is unusual in my experience: https://www.shutterstock.com/image-photo/impala-aepyceros-melampus-mediumsized-antelope-found-1560109979.

Stotting

Kobus kob kob has not, as far as I know, been recorded stotting. However, both K. k. thomasi and K. vardoni are known to stot, indicating a similar gait in the nominate subspecies.

Aepyceros melampus does not stot, but instead kick-stots - unlike any other ungulate.

Bounding

Kobus kob kob differs from A. melampus in that it does not bound.

(The similarity shown in the following is misleading. Kobus vardoni here is stotting, instead of bounding like the accompanying A. melampus: https://www.dreamstime.com/stock-photos-leaping-safety-image1304613.)

Foot-stamping? https://www.inaturalist.org/observations/53963188

Deliberate jumping of fences

I lack information on the jumping of fences by K. k. kob. However, other reduncins are known to jump fences deliberately. This suggests a considerable difference, because A. melampus does not deliberately jump fences even as low as 1.2 m high.

REPRODUCTION AND GROWTH

Reproduction is far less seasonal in K. k. kob than in A. melampus.

Gestation is longer in K. k. kob (261-271 days, referring to sspp. other than K.k. kob) than in A. melampus (190-210 days).

This is despite the fact that neonates are less massive in the former (4-5 kilograms in ssp. other than K. k. kob) than in the latter (4-5.5 kilograms).

The hiding period of infants is longer in K. k. kob than in A. melampus.

Overall, these results show K. k. kob to be considerably less precocial than A. melampus.

DISCUSSION

In both K. k. kob and A. melampus, olfactory communication for sociosexual purposes seems to be downplayed, relative to most ruminants.

Remaining glands (inguinal and possibly subauricular in the former, metatarsal in the latter) may function mainly in an anti-predator context (https://www.inaturalist.org/posts/39738-contrary-to-field-guide-books-reedbucks-redunca-spp-do-not-flag-the-tail-in-alarm#).

Reuncins are the tribe of bovids most associated with marshes. Where Kobus vardoni overlaps ecologically with A. melampus, it tends to range farther from trees on to alluvial plains. However, K. k. kob may be the form of Kobus most emancipated from the immediate vicinity of water, and most tolerant of woody vegetation. If so, this would indicate a degree of functional convergence with A. melampus, in complete allopatry.

Kobus vardoni replaces Kobus kob south of the equator. It is not mutually exclusive with A. melampus (https://www.alamy.com/stock-photo-female-pukus-kobus-vardonii-south-luangwa-national-park-zambia-africa-39497721.html?imageid=7E82250C-B634-4F0F-9872-EEEB91491767&p=57165&pn=2&searchId=4aa2a2926913d9b8b13ab0d4859d139f&searchtype=0 and https://www.alamy.com/stock-photo-female-pukus-kobus-vardonii-south-luangwa-national-park-zambia-africa-39497355.html?imageid=88083A61-D16A-4696-8DCD-B45DEE65E7D9&p=57165&pn=2&searchId=4aa2a2926913d9b8b13ab0d4859d139f&searchtype=0).

However, K. vardoni

• is stockier and much more massive than K. kob (https://www.alamy.com/kobus-vardonii-puku-south-luangwa-nationalpark-zambia-image61619641.html), with relatively short horns (https://www.mediastorehouse.com.au/ardea-wildlife-pets-environment/puku-south-luangwa-valley-national-park-zambia-1310255.html), and
• possesses interdigital glands, unlike both K. k. kob and A. melampus.

Kobus vardoni is also more plain-coloured (https://www.inaturalist.org/observations/168158234) than K. k. kob, with

• the pedal flag negligible (https://www.gettyimages.com.au/detail/photo/puku-luangwa-national-park-zambia-habitat-is-royalty-free-image/128122833), and
• an incipient/residual band on the ventral edge of the flanks (https://www.shutterstock.com/image-photo/wildlife-chobe-national-park-botswana-2222434941 and https://www.mediastorehouse.com.au/flpa/puku-kobus-vardonii-adult-male-10086820.html).

These differences indicate ecological separation between K. vardoni and A. melampus, allowing their partial sympatry.

Posted on March 14, 2024 01:32 AM by milewski