Paper on hybrid lions

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www.ias.ac.in/currsci/sep252008/720.

 

 

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OPINION

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CURRENT 720 SCIENCE, VOL. 95, NO. 6, 25 SEPTEMBER 2008

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Lions in India – A question of survival

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Nicky K. Xavier

 

A question uppermost in the mind of a

 

conservationist who is anxious for the

 

survival of lions in India should be whether

 

there is any necessity of keeping Asiatic

 

lions (Panthera leo persica) and their

 

Afro-Asian hybrids sequestered in zoos

 

on the grounds of maintaining purity of

 

genes. Will a thorough scientific study of

 

the morphology, morphometry, osteology

 

and genetic attributes and animal behaviour

 

necessarily lead to the conclusion

 

that dissimilarities between the two socalled

 

sub-species outnumber the similarities

 

between them? The answer should

 

be in the negative. It is often pointed out

 

that the Asiatic lion has a smaller mane

 

and a tendency to have a ventral skin

 

fold, is slightly smaller in size and lives in

 

smaller prides. Some have also gone to

 

the extent of asserting that when considering

 

its history and phylogeny, it must be

 

considered an evolutionary significant

 

unit, almost certainly on its way to becoming

 

a distinct species.

 

It appears, the logic of speciation is

 

not correct here. A narrow taxonomical

 

perspective based on minor differences

 

seems responsible for sequestration of

 

hybrids. These minor differences and

 

geographical isolation, on closer study, can

 

be found to be inadequate to justify such

 

separation and to wedge apart the lions

 

into different sub-species. For one thing,

 

reproductive isolation is conspicuously

 

absent in the African lions and their Indian

 

counterparts. Most of their progeny have

 

proved to be healthy and fertile. For another,

 

the differences pointed out are minor

 

phenotypic and behavioural ones, which

 

however are produced by evolutionary

 

changes in gene expression. Epigenetic

 

differences arise even in monozygotic

 

twins. Thirdly, one should also take note

 

of the similarity in the karyotypes of the

 

two populations. Fourthly, merging of

 

phenotypic traits inherited from the parents

 

in successive generations F1, F2, F3

 

and so on of the hybrids makes it difficult

 

even for experienced zookeepers to

 

make out the differences by appearance.

 

This shows that the rate of evolution in

 

lions is minimal and slower than what is

 

assumed to be in geographically isolated

 

populations.

 

For a conservationist what is important

 

is to conserve the species as a whole rather

 

than keeping them reproductively isolated

 

as sub-species on the basis of marginal

 

differences. It is not suggested here

 

that two distant species should be allowed

 

to cross-breed, resulting in loss of

 

biodiversity. What is emphasized is the

 

necessity of re-examining the definition

 

of sub-species, which forcibly keeps two

 

populations of the same species reproductively

 

isolated on the basis of superficial

 

differences and isolation of the

 

habitat. There is an increasing tendency

 

for taxonomists in general to divide a

 

sibling species into sub-species and not

 

unite them if required. Take, for example,

 

the swamp deer in India (Cervus duvaucelli).

 

At present there are three subspecies

 

differentiated on the basis of minor

 

phenotypic and habitat differences. If

 

these three populations are allowed to

 

mix, much of the danger surrounding their

 

survival can be averted. All this redounds

 

to the conclusion that there has to be a

 

paradigm shift in speciation and substructuring.

 

Chances of survival of the species as a

 

whole and genetic variability within the

 

population are enhanced by hybridization.

 

Introgression of genes will accelerate

 

recombination and the genes will be

 

differentially regulated according to newly

 

evolving surroundings. The surplus hybrid

 

lions in Indian zoos exemplify this. Even

 

though heterosis is not invariably found

 

in successive generations of all the animal

 

groups, most of the hybrid lions are found

 

to be healthy and well-adapted. This

 

means, our concern should only be to

 

maintain an optimum level or a proper

 

balance between inbreeding and out-breeding

 

of different populations of lions in

 

general.

 

In fact, hybrids began to come into being

 

in India mainly because African lions

 

inducted by circuses and leading a pathetic

 

life in small cages were confiscated

 

and confined by the Indian authorities in

 

various zoos, where they inadvertently

 

hybridized with captive Asiatic lions.

 

Captive lions with around 600 individuals

 

outnumber the lions in the wild in Gir

 

forest in Gujarat totalling 359 in number.

 

The majority of these captive individuals,

 

except in Chhatbir zoo, Punjab, where

 

some individuals have been found to be

 

ailing from certain neurological problems,

 

is reported to be hybrids that continue to

 

breed well and remain well-adapted to

 

Indian conditions as is evident from the

 

data now available with the Central Zoo

 

Authority. Neurological problems need

 

not necessarily be due to hybridization.

 

Such problems are observed even among

 

direct descendants of Asiatic lions from

 

Gir forest, kept at Sakkarbaugh zoo in

 

Gujarat as well. On the other hand, the

 

strenuous efforts to propagate Gir lions

 

in captivity or in zoos yield not so encouraging

 

results. Now the question is: will

 

the growing numbers of the captive lions

 

become burdensome to the authorities?

 

Statistics indicates that approximately Rs

 

60 million is spent annually on the upkeep

 

of all the lions, which includes hybrids

 

and pure Indian lions in zoos.

 

Surplus lions could be introduced into

 

selected sanctuaries, say at Kuno in

 

Madhya Pradesh or Chandraprabha in Uttar

 

Pradesh along with habitat restoration

 

programmes. It has been pointed out that

 

there remains a technical snag that a new

 

introduction of hybrids may not be permissible

 

under IUCN guidelines, which

 

were framed for re-introduction programmes.

 

Moreover, they do not consider the

 

hybrid lions as endangered or threatened

 

species. As pointed out above, the authorities

 

should start treating these animals

 

as intra-specific hybrids of two distant

 

populations, which still retain close affinities,

 

in the larger interest of the efficient

 

management of the teeming lions.

 

Apart from this, merging of phenotypic

 

traits inherited from the parents in successive

 

generations of hybrids shows that

 

the rate of evolution is minimal and slower

 

than what is assumed to be, especially in

 

these geographically isolated lion populations.

 

Otherwise, their separation may

 

not be as old as thought to be in the timescale.

 

The release of the lions into new

 

sanctuaries could be in a phased manner,

 

monitoring the released animals. However,

 

it must be concluded that once experimentally

 

released into the wild, the

 

question whether they will freely intermix

 

and form mixed prides mingling

 

with the Asiatic lions is yet to be ascertained

 

on empirical facts. If they do, one

 

can categorically conclude that geographical

 

separation has not led to the

 

formation of a so-called sub-species. What

 

OPINION

 

CURRENT SCIENCE, VOL. 95, NO. 6, 25 SEPTEMBER 2008 721

 

is therefore required now is the urgent

 

introduction of the hybrid population,

 

which is already having a wider gene

 

pool than their ancestral groups did, into

 

a new sanctuary as an experimental group

 

along with a habitat restoration programme

 

to be strictly monitored at least

 

in the initial stages.

 

One may note that another sanctuary is

 

proposed with the contingency of excess

 

numbers in zoos in mind. There is no

 

scope for fear that their numbers will

 

overshoot in the wild, because the natural

 

phenomenon of environmental resistance

 

will increase alongside population

 

size, and the latter will drop back as it

 

nears the carrying capacity. In the zoos,

 

contraception methods could be utilized

 

in the eventuality of excess growth of

 

numbers among the individuals of the

 

remainder left behind. In the wild, lions

 

can survive by predation. Yet at present,

 

their numbers are far less than the optimum

 

that our forests can sustain. In zoos

 

maintenance of big carnivores is questioned

 

sometimes from the point of view

 

of the ethical dilemma of killing some

 

animals to feed others. As pointed out

 

above, lions kill to survive. This natural

 

right of the carnivores is not lost simply

 

by reason of their captivity in zoos. Domestic

 

animals which profusely breed and

 

multiply in farms and which are common

 

should be given less importance than the

 

critically endangered tertiary level of

 

carnivores, which must be conserved at

 

any cost.

 

There has been a suggestion from some

 

quarters that hybrids should be culled

 

away. One can never support culling

 

healthy and genetically appropriate lions.

 

Culling of healthy animals which have

 

come into existence because of man’s activism

 

is not appreciated all over India,

 

where the lion is an object of worship

 

and forms part of mythology, folklore

 

and the state currency. Even if genetically

 

inappropriate and sterile inter-specific

 

hybrid animals like ligons or tigons were

 

to come into being by wrong breeding

 

practices in zoos, the idea of culling

 

would still be abhorrent to the Indian

 

ethos and they would be magnanimously

 

allowed to complete their lifetimes. Coming

 

to individuals stricken down with incurable

 

illness in Indian zoos, euthanasia

 

is resorted to in order to put an end to the

 

suffering. A total extermination of the

 

hybrids, if suggested is a horrible, unscientific

 

proposition, to say the least.

 

According to some assumptions, conservation

 

of biodiversity rules out man’s

 

intervention, and the purity of African

 

lions and Asiatic lions should be left untouched.

 

But there have been several instances

 

in which man has intervened to

 

preserve the gene pool. It has been reported

 

that when natural hybridization

 

was widespread, the US authorities intervened

 

in order to save the red wolf, even

 

as their hybrids were brought under conservation

 

programme. Also natural calamities

 

like floods, droughts and wild fires

 

have prompted man to intervene to protect

 

endangered animals, as has been the case

 

in Northeast India, where artificial

 

mounds are built during monsoons so

 

that wild animals, including rhinos might

 

take shelter from the rising waters of the

 

River Brahmaputra. When fragmentation

 

of habitats took place, the Government

 

took the initiative to build forest corridors

 

linking different segments together, thus

 

facilitating conspecific hybridization.

 

Man’s intervention in nature, an inevitable

 

feature of his struggle for survival, is a

 

fait accompli and it is futile to shy away

 

from it at this point of time when conservation

 

of animal populations is at stake.

 

Despite the fact that among human

 

populations there are marked differences

 

in phenotype, genotype and behavioural

 

patterns across the continents, they have

 

not been treated as separate sub-species.

 

No authority has forced on them the law

 

for reproductive isolation as a measure to

 

maintain genetic diversity. Then why,

 

scientifically speaking, a different standard

 

for animals when man himself is an

 

animal?

 

Nicky K. Xavier lives at Kollannur

 

House, Patturaikkal, Thrissur 680 022,

 

India. e-mail: nickyxavier

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