Inbreeding in Big Cats: Consequences and Conservation

[Balam]

@peter and I wanted to bring this subject forward to the forum.

In the realm of majestic big cats, the threat of inbreeding silently looms, casting a shadow on their genetic diversity and survival. Inbreeding, a phenomenon of breeding closely related individuals within a population, carries far-reaching implications for the morphology and health of these magnificent creatures. In this post, we will delve into the intricacies of inbreeding, explore its causes, examine documented instances, discuss its ramifications, and shed light on how biologists can play a crucial role in preventing this peril.

What is Inbreeding and Why Does It Occur?
Inbreeding involves the reproduction between relatives, often leading to an increase in homozygosity – the presence of identical alleles for a particular trait. This can expose detrimental recessive alleles, causing a range of health issues and reducing overall genetic diversity. In the wild, factors such as habitat fragmentation, small population sizes, and geographic isolation can contribute to inbreeding as natural genetic mixing becomes limited.

Recorded Instances and Consequences:
Documented cases of inbreeding among big cat species serve as stark reminders of its consequences. For instance, the Amur tiger population in Russia faced a critical genetic bottleneck due to excessive hunting, resulting in a small founder population and increased inbreeding. In captivity, the infamous example of the Asiatic lion population at the Gir Forest National Park in India illustrates the dangers of a limited gene pool. Inbreeding depression, manifested through reduced reproductive success, weakened immune systems, and decreased overall fitness, threatens the long-term survival of these iconic species.

Impact on Morphology:
Inbreeding often leads to the expression of deleterious traits, affecting the morphology of big cats. Physical abnormalities, such as congenital disorders, unusual coat patterns, and skeletal deformities, can emerge as a result of the loss of genetic diversity. These traits not only compromise the health of individual animals but also hinder their ability to thrive in their natural environments, impacting their chances of survival and reproduction.

Conservation Efforts and Preventive Measures:
Biologists and conservationists play a pivotal role in combatting the threat of inbreeding. Implementing managed breeding programs that prioritize genetic diversity and minimize the risk of inbreeding can help restore the health of struggling populations. Techniques such as introducing carefully selected individuals from other populations, monitoring genetic health, and promoting gene flow can aid in maintaining the genetic vitality of big cat species.

As we delve into the causes, effects, and potential remedies for inbreeding, a compelling inquiry emerges: do biologists and conservationists truly possess the key to unlocking a brighter future for these majestic creatures? Can collaborative endeavors and strategic interventions effectively shield the invaluable genetic diversity that fuels the vigor of big cat populations for generations to come? The path forward rests not only on scientific understanding but on the collective determination to address this challenge and secure the legacy of these remarkable animals. Reply

[peter]

ALL

I've not much to add to Balam's lead post, as it covers just about all of it.

This thread was created to inform our members and readers about inbreeding in wild big cats. Inbreeding is a very real problem, because the world is rapidly changing. I'm referring to the continuing growth of the human population, the loss of wild country, climate change, poaching, population fragmentation, a lack of corridors, the dwindling numbers of prey animals, politics and all the rest of it. The question is what the impact of these factors is for those making their home in the natural world. 

Big cats are apex predators, meaning they'll be the first to suffer when the conditions change. Example. 

In the last decades, poaching developed into a problem of significant proportions in many regions in southeast Asia. The forest is still there, but it's loaded with snares and, therefore, largely empty. The result is tigers, protection or no protection, are all but gone. In Sumatra and Malaysia, they're severely struggling. Amur tigers recovered after the population bottleneck of the previous century. Journalists, magazins and those involved in documentaries noticed, but so did poachers. Recent information (referring to an article in the National Geographic in January 2022 in particular) strongly suggests poaching is developing into a very real problem in the Russian Far East once again. 

Tigers are not the only big cats that suffer. In most wild regions, big cats struggle to make ends meet. And that's still without inbreeding. 

The time to discuss the problem has arrived, that is. 

I recently got a link to an article about the impact of inbreeding in wild lions. If I remember correctly, it was posted by 'Wild at heart', a new member. I'll ask BAO, who informed me about the article, to guide you to the thread in which the article was posted. According to BAO, the contributions of our new member are well worth your time. 

Here's the link to the article. Interesting read:            

https://cbs.umn.edu/sites/cbs.umn.edu/fi...ongoro.pdf Reply

[Pckts]

Inbreeding/line breeding is a natural occurrence. Neither good nor bad. While bad traits and immune responses are doubled the good traits are as well. Especially with line breeding which is why you saw such a strong population in Tadoba from Wagdoh lineage and Machli in Ranthambore. 
You always want new blood which may offer stronger and different immune responses but they also may bring in bad blood that dilutes an otherwise strong population. Reply

[Balam]

(08-23-2023, 09:28 PM)Pckts Wrote: Inbreeding/line breeding is a natural occurrence. Neither good nor bad. While bad traits and immune responses are doubled the good traits are as well. Especially with line breeding which is why you saw such a strong population in Tadoba from Wagdoh lineage and Machli in Ranthambore. 
You always want new blood which may offer stronger and different immune responses but they also may bring in bad blood that dilutes an otherwise strong population.

Have the tigers from this area been the subject of genetic studies to assess the level of inbreeding and genetic health? You do bring an interesting point in regards to line breeding which typically involves mating animals that are related, but not as closely related as in traditional inbreeding. The thing is that this is an entirely controlled practice that we can't happen in the wild with the same rigour it does in captivity.
 
The case that sparked this conversation with the jaguars being reintroduced into the Iberá wetlands represents direct inbreeding which can cause a serious genetic bottleneck down the line, even if the animals inbreeding may appear superficially very healthy.

This is why in areas where populations of animals are isolated and not connected through natural corridors the risk of extinction increases, because inbreeding make their immune system weaker, drops their fertility, and increases mortality. Constant inbreeding also causes a reduction in size from successive generations and may be one of the reasons why Amur tigers and Asiatic/West African lions do not achieve the same consistency in large sizes the may have in the past (in addition to precarious prey base). It's also specially worrying in the case of the lions because in theory a virus or disease can be lethal to the population in Gir given their possibly weaker immune systems. We are seeing this in the way the sperm of Asiatic lion has deteriorated due to inbreeding, which makes us wonder to what degree this has also occurred in Amur or Sumatran tigers.

"Fitzpatrick and colleague Jonathan Evans compared existing data on sperm fitness for 20 endangered and non-endangered species of mammals, including the Florida panther, Asiatic lion and cheetah. Scientists have previously observed extreme reductions in sperm quality for each of these big cats – all of which also suffered huge reductions in population size that led to inbreeding.


The team found that, on average, 48% of the sperm of endangered species was abnormal, compared with 30% in non-endangered species. In addition, the percentage of the sperm that was motile – or capable of movement – was around 10% lower in endangered species. Earlier research has shown that both characteristics make a male less likely to produce viable offspring."

More here. Reply

[Pckts]

(08-23-2023, 11:31 PM)Balam Wrote:

(08-23-2023, 09:28 PM)Pckts Wrote: Inbreeding/line breeding is a natural occurrence. Neither good nor bad. While bad traits and immune responses are doubled the good traits are as well. Especially with line breeding which is why you saw such a strong population in Tadoba from Wagdoh lineage and Machli in Ranthambore. 
You always want new blood which may offer stronger and different immune responses but they also may bring in bad blood that dilutes an otherwise strong population.

Have the tigers from this area been the subject of genetic studies to assess the level of inbreeding and genetic health? You do bring an interesting point in regards to line breeding which typically involves mating animals that are related, but not as closely related as in traditional inbreeding. The thing is that this is an entirely controlled practice that we can't happen in the wild with the same rigour it does in captivity.
 
The case that sparked this conversation with the jaguars being reintroduced into the Iberá wetlands represents direct inbreeding which can cause a serious genetic bottleneck down the line, even if the animals inbreeding may appear superficially very healthy.

This is why in areas where populations of animals are isolated and not connected through natural corridors the risk of extinction increases, because inbreeding make their immune system weaker, drops their fertility, and increases mortality. Constant inbreeding also causes a reduction in size from successive generations and may be one of the reasons why Amur tigers and Asiatic/West African lions do not achieve the same consistency in large sizes the may have in the past (in addition to precarious prey base). It's also specially worrying in the case of the lions because in theory a virus or disease can be lethal to the population in Gir given their possibly weaker immune systems. We are seeing this in the way the sperm of Asiatic lion has deteriorated due to inbreeding, which makes us wonder to what degree this has also occurred in Amur or Sumatran tigers.

"Fitzpatrick and colleague Jonathan Evans compared existing data on sperm fitness for 20 endangered and non-endangered species of mammals, including the Florida panther, Asiatic lion and cheetah. Scientists have previously observed extreme reductions in sperm quality for each of these big cats – all of which also suffered huge reductions in population size that led to inbreeding.


The team found that, on average, 48% of the sperm of endangered species was abnormal, compared with 30% in non-endangered species. In addition, the percentage of the sperm that was motile – or capable of movement – was around 10% lower in endangered species. Earlier research has shown that both characteristics make a male less likely to produce viable offspring."

More here.

If Predators are isolated they are more susceptible to extinction due to many factors. Their prey suffers the same as they do, the slightest imbalance can cause catastrophic outcomes. But when all things are equal, linebreeding and inbreeding occur often, I mention Waghdoh because Tadoba is filled with his progeny, the same with Ranthambore and Machli and any other place with a long standing dominate male/female. 
But like I said, it must be a balance, you always want new blood to introduce possible traits that could be beneficial but that new blood can be detrimental as well. 
There would be no dog breed today without inbreeding and linebreeding, humans followed this same pattern and it never affected their population increase. 
 
Point being, when you see a big, strong male cat you want his genes spread. You want him line bred throughout the territory and that's what happens, it's the natural cycle. Occasionally a new male comes in, runs him out and introduces his genes in hopes to accomplish the same. Whether this new male brings a positive result or negative one is completely random. Reply

[Balam]

(08-18-2023, 10:50 PM)BA0701 Wrote: The following post was shared by @Wyld@Heart in another thread, provides us with a wealth of information about the Crater Lions, and the impact that the lack of genetic diversity is having on the population. 

Wyld@Heart's original post:

"There have been, the ones I know of are specific to lions of Ngorongoro where inbreeding is pretty much unavoidable. 

https://conbio.onlinelibrary.wiley.com/d....tb00127.x

https://www.google.com/url?sa=t&source=w...WjFlv8FEj0

I hope the links work. There are also a few others about. Some 'light' reading, haha."


The first link, conbio, is a short informative abstract of a case study written by C. PACKER, A. E. PUSEY, H. ROWLEY, D. A. GILBERT, J. MARTENSON, S. J. O'BRIEN, and the second link is the full study. This study combines information on two subjects I have long been fascinated with, Crater Lions and the impact of inbreeding on the wild lion population. 

The abstract states:

Abstract: Lions in the Ngorongoro Crater, Tanzania, form a small and naturally isolated population. In 1962, the Crater lions suffered an epizootic that reduced the population to nine females and one male. An additional seven males apparently immigrated into the Crater in 1964–1965, but there has been no further immigration into the Crater in the past 25 years. By 1975, the population had recovered to its current level of 75-125 animals. All members of the current Crater population are descended from only 15 founders, and over the years there has been considerable variance in the reproductive success of both sexes. The Crater was probably colonized by lions from the nearby Serengeti ecosystem and the contemporary Crater lion population shows a significant lack of genetic diversity compared to the much larger Serengeti population. The detailed reproductive history of the Crater population was incorporated into a series of stochastic computer simulations that generated distributions of expected allele frequencies under different sets of initial conditions. The simulations suggest that the Crater population may have passed through previous bottlenecks before 1962 but that the level of heterozygosity in the breeding population has been declining since the mid-1970s, regardless of the population's genetic composition in the 1960s. High levels of inbreeding are correlated with increased levels of sperm abnormality in lions and there is evidence that the reproductive performance of the Crater lions has decreased as a result of decreasing heterozygosity.

Bringing this here from the Tanzania lion thraed. @peter is this the recent study you were referring to? It is the same one I linked before from Packer, I specially like this excerpt from the study:

High levels of inbreeding are correlated with increased levels of sperm abnormality in lions and there is evidence that the reproductive performance of the Crater lions has decreased as a result of decreasing heterozygosity.

It shows that despite their impressive superficial physiques, these lions are clearly suffering internally from the high degrees of inbreeding. Additionally, it also highlights how much inbreeding can affect a population's fertility and therefore long-term survival. From the Kope Lion, the arrival of new blood in the form of a single coalition was all in took for the fertility of the area to skyrocket following decades of familial breeding:

*This image is copyright of its original author

In their articile they mention the Corridor of Tolerance which is an innitiative they've undertaken with local tirbes to increase the connecivity between northern Tanzanian and southern Kenya in the Greater Serengeti Ecocystem to reestablish lion populations in areas where Maasai tribes have historically persecuted and exterminated lion populations, which has been the main cause for the lack of connectivity between lions from the crater and the Serengeti, isolating those form the Ngorongoro crater and increasing heterozygosity between them. It's clear that the lions from the Ngorongoro crater are part of the same population as those from the rest of the Greater Serengeti, they just have not been properly connected to them due to fragmented corridors for decades:

*This image is copyright of its original author

With four new coalitions being described as having arrived to the crater from the Serengeti since the inception of this program, a new study on the changes to the fertility rates and health of the Ngorongoro population will be needed to asses just how much they've affected the population. This corridor is an amazing and life-saving initiative for these lions. Reply

[BA0701]

(08-25-2023, 11:16 PM)Balam Wrote:

(08-18-2023, 10:50 PM)BA0701 Wrote: The following post was shared by @Wyld@Heart in another thread, provides us with a wealth of information about the Crater Lions, and the impact that the lack of genetic diversity is having on the population. 

Wyld@Heart's original post:

"There have been, the ones I know of are specific to lions of Ngorongoro where inbreeding is pretty much unavoidable. 

https://conbio.onlinelibrary.wiley.com/d....tb00127.x

https://www.google.com/url?sa=t&source=w...WjFlv8FEj0

I hope the links work. There are also a few others about. Some 'light' reading, haha."


The first link, conbio, is a short informative abstract of a case study written by C. PACKER, A. E. PUSEY, H. ROWLEY, D. A. GILBERT, J. MARTENSON, S. J. O'BRIEN, and the second link is the full study. This study combines information on two subjects I have long been fascinated with, Crater Lions and the impact of inbreeding on the wild lion population. 

The abstract states:

Abstract: Lions in the Ngorongoro Crater, Tanzania, form a small and naturally isolated population. In 1962, the Crater lions suffered an epizootic that reduced the population to nine females and one male. An additional seven males apparently immigrated into the Crater in 1964–1965, but there has been no further immigration into the Crater in the past 25 years. By 1975, the population had recovered to its current level of 75-125 animals. All members of the current Crater population are descended from only 15 founders, and over the years there has been considerable variance in the reproductive success of both sexes. The Crater was probably colonized by lions from the nearby Serengeti ecosystem and the contemporary Crater lion population shows a significant lack of genetic diversity compared to the much larger Serengeti population. The detailed reproductive history of the Crater population was incorporated into a series of stochastic computer simulations that generated distributions of expected allele frequencies under different sets of initial conditions. The simulations suggest that the Crater population may have passed through previous bottlenecks before 1962 but that the level of heterozygosity in the breeding population has been declining since the mid-1970s, regardless of the population's genetic composition in the 1960s. High levels of inbreeding are correlated with increased levels of sperm abnormality in lions and there is evidence that the reproductive performance of the Crater lions has decreased as a result of decreasing heterozygosity.

Bringing this here from the Tanzania lion thraed. @peter is this the recent study you were referring to? It is the same one I linked before from Packer, I specially like this excerpt from the study:

High levels of inbreeding are correlated with increased levels of sperm abnormality in lions and there is evidence that the reproductive performance of the Crater lions has decreased as a result of decreasing heterozygosity.

It shows that despite their impressive superficial physiques, these lions are clearly suffering internally from the high degrees of inbreeding. Additionally, it also highlights how much inbreeding can affect a population's fertility and therefore long-term survival. From the Kope Lion, the arrival of new blood in the form of a single coalition was all in took for the fertility of the area to skyrocket following decades of familial breeding:

*This image is copyright of its original author

In their articile they mention the Corridor of Tolerance which is an innitiative they've undertaken with local tirbes to increase the connecivity between northern Tanzanian and southern Kenya in the Greater Serengeti Ecocystem to reestablish lion populations in areas where Maasai tribes have historically persecuted and exterminated lion populations, which has been the main cause for the lack of connectivity between lions from the crater and the Serengeti, isolating those form the Ngorongoro crater and increasing heterozygosity between them. It's clear that the lions from the Ngorongoro crater are part of the same population as those from the rest of the Greater Serengeti, they just have not been properly connected to them due to fragmented corridors for decades:

*This image is copyright of its original author

With four new coalitions being described as having arrived to the crater from the Serengeti since the inception of this program, a new study on the changes to the fertility rates and health of the Ngorongoro population will be needed to asses just how much they've affected the population. This corridor is an amazing and life-saving initiative for these lions.

It is a very informative, fascinating, and thorough study, introduced to me by our member @Wyld@Heart , and definitely recommended reading for anyone interested in the subject of the impact inbreeding has on wild populations. The fact that they can trace back every lion in the Crater to the original 15 is incredible. In fact, a large part of the population was repopulated, following a plague, in large part by descendants of  4 females who were born in the Crater in 1957. While a relatively small population, their common ancestry can be traced back decades. The corridor, as @Balam mention, was an absolute necessity to preserving this population.

While the Crater Lions have a very healthy and unique looking appearance, it has been explained to me that these qualities are largely the result of an abundance of prey animals, combined with the low number of lions residing in the area. Perhaps there is more to it than that, as is the case in zoo cats, which also typically share unique facial features, the result of inbreeding. Could it be possible that it is having an impact on the Crater cats in the same way? Reply

[Pckts]

The crater is a completely unique landscape and a relatively small area. It’s only going to house so many lions and generally lions can come and go as they please although most chose to stay if they can due to the year round prey source, water and cooler climates. 
The only real unique appearance for Lions there is the shoulder mane which is due to the cooler temps and their bigger girth which comes from the more abundant prey.
But you can see lions coming and going in the crater all the time, it’s not difficult for them to get in and out. Masai still walk their cattle in every day to graze.
I’ve been there btw, it’s a stunning place. Reply