Indian mole-rat could hardly be more different from southern African mole-rats
(writing in progress)
Mole-rats are interesting for various reasons.
One reason is that there has been ostensibly convergent evolution among various lineages of mole-rats on various continents.
Another is that these animals provide an extreme example of disturbance of the substrate, effectively tilling and fertilising soils for plants.
And of course, it is well-known that extreme forms of mole-rats, particularly the naked mole-rat (Heterocephalus, https://www.inaturalist.org/taxa/43746-Heterocephalus-glaber) of the Horn of Africa, live extremely long, breed extremely slowly, and have developed the closest thing to eusociality in mammals.
I have mentioned in other Posts how odd it is, given the repeated evolution of mole-rats on various continents and the widespread distribution of several families of mole-rats in Africa, that there is no mole-rat to speak of in India.
The purpose of this Post is to clear up any possible confusion about the presence of mole-rats in India. After all, a species called the ‘Indian mole-rat’ is widespread and abundant in India, and also occurs in Java - another intensely cultivated part of Asia.
The Indian mole-rat (Bandicota bengalensis, https://www.inaturalist.org/taxa/45665-Bandicota-bengalensis) is misnamed. This is because the only ways in which it resembles true mole-rats are its ability to burrow extensively, and its storage of food underground. Apart from these habits, it is every bit a normal rat. Indeed, it seems to be as good an example of a commensal species as the familiar rats (e.g. Rattus norvegicus,https://www.inaturalist.org/taxa/44576-Rattus-norvegicus) of the genus Rattus itself.
Bandicota bengalensis
https://www.inaturalist.org/observations/102974768
https://www.inaturalist.org/observations/42322447
https://www.inaturalist.org/observations/40283635
https://www.inaturalist.org/observations/39917553
Bandicota Indica
https://www.inaturalist.org/observations/97326296
https://www.inaturalist.org/observations/48544040
https://www.inaturalist.org/observations/38322634
https://www.inaturalist.org/observations/22067844
https://www.inaturalist.org/observations/93684018
Bandicota savilei
https://www.inaturalist.org/observations/119248280
https://www.inaturalist.org/observations/99449108
The Indian mole-rat lives in cultivated areas. It functions as a typical rat that has adapted to the exposure of its extremely productive but seasonally bare habitat by digging tunnels and storage chambers. It stores large quantities of grain underground. These are often retrieved by farmers in the non-growing season.
The Indian mole-rat, quite unlike African mole-rats (Bathyergidae, https://war.wikipedia.org/wiki/Bathyergidae), is extremely fecund and short-lived – as much as Rattus or even more so.
As I understand it, the individual lives for only about one year. During this time, it bear up to 10 litters, each consisting of up to 10 neonates.
On a scale of fecundity among ‘mole-rats’ on which the naked mole-rat scores 1, the Indian mole-rat scores 10. It is, in other words, extremely ‘r-selected’ (https://en.wikipedia.org/wiki/R/K_selection_theory).
So fecund, indeed, is the Indian mole-rat that I see it as a prime example of the intense co-evolution of various animals with humans in southern and southeast Asia. I suspect that cultivation first started in India up to 30,000 years ago, and that previous to this the species B. bengalensis did not exist. In other words, I suspect that the species B. bengalensis, if not its whole genus, is an extremely recent product of anthropogenic influence.
It is important to realise the following.
True mole-rats (e.g. the familiar Cryptomys of South Africa, https://www.inaturalist.org/taxa/43749-Cryptomys-hottentotus) are specialised for underground life,
- being nearly blind,
- having a reduced tail,
- metabolising slowly in an oxygen-poor environment,
- digging with the teeth, and
- foraging entirely underground by digging its way to tubers, rather than going to the surface and then digging down to the food items.
By contrast, the Indian mole-rat is merely fossorial. I.e. it forages above-ground, but merely – like so many other mammals of various orders – digs to create refuges. It is not specialised for underground life in any meaningful sense.
There is a lineage of rodents (in a different family, i.e. Spalacidae https://en.wikipedia.org/wiki/Spalacidae instead of Muridae) in India that more closely resembles true mole-rats, belonging to the genus Cannomys (https://www.inaturalist.org/taxa/45728-Cannomys-badius).
However, as I understand it, Cannomys is neither as specialised for underground life as are the African mole-rats, nor widespread in peninsular India. It occurs mainly in Indochina, and hardly reaches India. It forages partly above-ground, so is only ‘half-convergent’ with African mole-rats.
Therefore, true mole-rats of any family are in fact absent in India.
Given how typical mole-rats are of many biomes in Africa, the absence of similar rodents in India is a prime ecological and biogeographical puzzle.
This is, indeed, one of the most striking of differences in the mammalian communities in Africa and India. It has never been explained, because such rodents are highly expected based on the faunas of other parts of the world with similar climates, soils, and mammal communities.
My explanation would be that a long history of farming has profoundly affected the evolution of mammals in India, with the result that there is no real niche for mole-rats in India.
Bandicota bengalensis:
http://www.planet-mammiferes.org/drupal/en/node/40?indice2=Photos%2FRongeur%2FMyomo%2FMurine%2FBandBen5.jpg
Bandicota bengalensis:
http://www.planet-mammiferes.org/Photos/Rongeur/Myomo/Murine/BandBen4.jpg
Bandicota bengalensis:
http://maps.iucnredlist.org/map.html?id=2540
https://en.wikipedia.org/wiki/Bamboo_rat
https://www.inaturalist.org/observations?place_id=any&taxon_id=45663&view=species
Cannomys badius:
https://en.wikipedia.org/wiki/Lesser_bamboo_rat#/media/File:Cannomys_badius_Plzen_zoo.jpg
Cannomys badius:
https://www.inaturalist.org/observations/93684000
https://www.inaturalist.org/observations/55581344
(writing in progress)
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