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Tiger Demographic
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04-09-2016, 09:29 PM
( This post was last modified: 04-15-2016, 04:37 AM by Dr Panthera
Edit Reason: Intention could be misinterpreted
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In previous discussions with a few esteemed members of our forum I noticed that their understanding of tiger population demographics and variation among different population is focused on certain habitat, the main point was the variation of the percentage of breeding adult tigers in different habitat; in areas with quality habitat and adequate prey base tigers establish territories and breed continuously and have more cubs, consequently the percentage of juvenile tigers ( cubs, large cubs, and sub-adults) is high and juveniles outnumber adults, conversely in poor habitat tigers breed less, have less cubs, and their cubs and sub-adult survival is poor and adults may outnumber them.
A great study on this issue was authored by Barlow, McDougal, Smith, Gurung, Tamang and others based on long term data from Chitwan Royal National Park in Nepal. The authors classified tigers as breeding and non-breeding, breeding tigers are resident males and females who established territories and secured resources for successful reproduction. Non-breeding tigers were classified as cubs (0-1 year) large cubs (12 - 18 to 24 months the age of dispersal ) pre-territorial transient animals ( sub-adults looking to establish a territory ) and post-territorial transient ( adults that were forcefully ejected from their territory by stronger rivals). The data showed a stable number of breeding adults per study area...a 100 km2 area constantly had 8 breeding adults 1-2 males and 6-7 females , the litter size and survival of cubs was also somewhat stable, the biggest variable was the transient tigers. Resident males per population 0-15% Mean 7 % Resident females 23-67% Mean 35% Cubs 0-65% Mean 30% Large Cubs 0-55% Mean 18% Transients ( pre and post-territorial) 0-40% Mean 10% Consistent with large polygamous mammals male tigers need to be of a number small enough to curb competition and large enough to ensure genetic variability Breeding female tigers are the most important component of tiger society and hold the key to the species success. Their number is the most important predictor of survival in any tiger habitat census. Juveniles ( cubs and large cubs ) are the future of tigers and their survival to adulthood and success in establishing territories is very complex and dependent on the particular tiger demographics in the area, resources, and conservation. Transients young and old live stressful lives ..chased by territory holders, pushed towards fringe habitat, get in conflict with man and sadly die frequently from such encounters. 
I assume this is directed at me, since I was the one who questioned your claim of <1000 breeding adults in India. Do you know of any scientific study conducted in this regard in India or are you just extrapolating Chitwan's data to all of India?
In the documentary "Tigers of the Emerald forest" based in Panna National park in Northern India, narrated by Dr. Raghu Chundawat, the tigress Julie mated with both the territorial male Madla and a transient male Broken tooth, who sneaked upon her when Madla was on a patrol of his vast territory. Dr. Chundawat specifically mentioned that female tigresses often wander far and mate with several males when in heat. This behaviour was again observed in another documentary shot in Ranthambhore, where the tigress T-17 mated with male T-28 and then went out of her territory and mated again with the male T-25. No one knows who the father of her litter was, since she mated with both males. Another instance was observed in Bandhavgarh where the Bamera male was seen watching the old male Bokha mating with one of his tigresses. So we have recorded instances where tigresses mate with both territorial and transient males. So we cannot assume that transient males are not breeding males. Also, tigers can breed right till their old age. B2 fathered cubs even when he was more than 12 years old, so did charger. The recently deceased Baghin Nala female of Pench had produced her last litter at the age of 12. Now, the study you quoted says (taking the mean value), percentage of breeding adults is about 42%, but that is when counting small cubs, which make up 30% according to that study. India's census does not count that 30% small cubs. (It only counts the 70% population of adults and large cubs >1.5 years), and 42 is 60% of 70 . Considering some transient males also breed, that percentage would be even higher. So that would peg the number of breeding adults in India's case at >60% of 2200 which comes to >1320. While you said it was <1000. That was my whole point. 
Not to derail the thread but wasn't T17's cub from t28 since she originally mated with t25 for a while and was never able to get pregnant until t28 entered the mix then t25 fought her, possibly killed her then the Cubs were lost after that.
04-15-2016, 04:34 AM
( This post was last modified: 04-15-2016, 06:14 AM by Dr Panthera
Edit Reason: clarification
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(04-10-2016, 05:23 AM)Shardul Wrote: I assume this is directed at me, since I was the one who questioned your claim of <1000 breeding adults in India. Do you know of any scientific study conducted in this regard in India or are you just extrapolating Chitwan's data to all of India? No not really and I apologize if I sounded like that, in a nut shell whether the results of Chitwan ( and possibly all the Terai landscape) and the Sunderbans ( from M.Khan) or any tiger stronghold the pattern is the same: Tigers have cubs when the conditions are good and in the best habitat every breeding female is likely to have 2-4 cubs with her, so in good habitats the percentage of cubs and sub-adults will outnumber adults whereas in populations where tigers are decreasing in numbers and under a lot of pressure the majority will be adults. Some habitat in India are great others not so much so the breeding animals there could be as low as 800 and as high as 1500. that is not to say that a small isolated populations of tigers in India and elsewhere could be almost 100% adult...for sure but these populations will go extinct in less than ten tiger generations ( 35 years ) if the current trends continue. Similar trends are noticed in lions and leopards, and all mammals who have multiple young per litter, healthy populations breed successfully and have plenty of surviving cubs and sub-adults inflating their percentage in the population. Mating of transient animals is sporadic and occasional and can not be considered regular tiger behavior certainly where territorial male numbers are optimal but I agree that it happens more than previously expected. We need to intensify efforts for conserving tigers especially in tiger conservation units of first grade since they are the future of this amazing predator.
@Dr Panthera
I don't understand why you deliberately keep ignoring my main point. In India's case the % of breeding adults is higher because the Indian tiger census does NOT COUNT SMALL CUBS. Let me repeat it again INDIAN TIGER CENSUS DOES NOT COUNT SMALL CUBS. IT ONLY COUNTS TIGERS >1.5 YEARS OF AGE . The Chitwan study you quoted actually supports my assertion. It says in an entire tiger population, the % of breeding adults is 42% WHEN COUNTING SMALL CUBS WHICH MAKE UP 30%. Resident males per population 0-15% Mean 7 % Resident females 23-67% Mean 35% Cubs 0-65% Mean 30% Large Cubs 0-55% Mean 18% Transients ( pre and post-territorial) 0-40% Mean 10% So based on the Chitwan study that YOU QUOTED, % of breeding adults in a healthy tiger population is 60% WHEN NOT COUNTING SMALL CUBS. Let me repeat: [b]60% WHEN NOT COUNTING SMALL CUBS.[/b] So 60% of 2200 is 1320. Now, Tigers are not doing well all over India. Let me give you some examples: Chitwan-Parsa-Valmiki landscape. One contiguous forest patch in eastern Terai. However, Chitwan has almost a 100 tigers while Valmiki has less than 20, Both cover similar area. Corbett Tiger reserve in Western Terai: 200+ tigers in 2000 km2 Rajaji in Western Terai: <40 tigers in 900 km2 Dudhwa & Pilibhit in Central Terai: <100 tigers in 1600 km2 Simlipal in Eastern India: <30 tigers in 3000 km2 Kaziranga in Assam: 120 tigers in 800 km2 Manas in Assam: <30 tigers in 3000 km2 The Gist: India's tiger population is divided in a lot of fragmented small habitats, not all of which are doing well. Some areas have high prey density and protection, others have sub-optimal prey density and low protection. Some have high poaching incidents , some have low. Others are in between. So some will have more % of cubs and subadults, others will have low. So considering this scenario and atleast some transient breeding males, the % is higher than 60. i.e >1320 breeding adult tigers. To the Mods: Sorry for the caps and bold text, I didn't know what else to do.
In regards to breeding by transient animals Barlow et al. considered it negligible possibly because:
* Transient females have limited access to prime denning sites and to prey and have more conflict with man. * Transient males may mate with resident females if the territorial males occupy an area larger than their patrolling ability, in marginal habitat males have to occupy a larger area and transient males can fringe on their territory and mate with receptive females, add to this that the territorial male will still have to feed himself and hunt. In prime habitat the territorial male will chase the transient ones more likely. Compare this in prime lion habitat where males can devote most of their time to patrolling and protecting their turf and less to acquiring food. In both species though females do not restrict their reproductive partners to resident animals all the time and factors affecting this rare yet remarkable female behavior are still not fully known yet "attraction" of females to presumably "inferior tranisent/nomadic males" can still be seen. (04-15-2016, 06:16 AM)Shardul Wrote: @Dr PantheraPrecisely the point !! Some habitat are great and the juvenile population will outnumber the adults significantly and in others there are virtually no young animals. The census figure is made up of juvenile tigers between 18 months and 4 years ( non-breeding) post-prime adults (non-breeding) and resident prime aged animals (breeding) altogether 2200 animals, depending on condition between a third to two thirds of these older animals MAY HOLD A TERRITORY AND HAVE ENOUGH PREY TO BREED so we can have 750 breeding animals and we can have 1500 animals. As you know in many poor habitat resident tigers are not breeding tigers. So you are an optimist and I salute you for that, accept 1320 or 1500 or more, I would like us to be able of dealing with the worst case scenario for wildlife because it is credible and dangerous, and I have seen in my lifetime the extinction of three tiger ecotypes while government officials and safari operators are trumpeting success. Real tiger numbers are less than 3800 and not 7000, lions are likely to be closer to 20000 than 39000 and leopards are definitely below 100000 it is a grim fact. My main point again is that we can not put a price on a breeding female of an endangered species.
I am not being an optimist at all. An overall higher percentage of sub adults would mean the conditions are excellent, which is far from true. Common problem in India is when a reserve reaches it's carrying capacity of tigers, the sub adults disperse out, lose protection and get killed by humans. The 'source' population remains the same, the extra animals dispersing out have no 'Sink Areas' that can absorb them. Take Ranthambhore for eg, even with the best protection and prey available, it cannot carry 100 tigers. It currently has about 35 and that will remain stable more or less. The resident tigers will keep breeding and the dispersing animals will keep dying if they do not find a suitable habitat outside ranthambhore. Other areas with lesser protection have animals being killed around and some times inside the reserves. Tigers are prolific breeders. Give them enough prey and protection and their population will rebound in no time.
Manas in Assam: <30 tigers in 3000 km2
Simlipal in Eastern India: <30 tigers in 3000 km2 Rajaji in Western Terai: <40 tigers in 900 km2 Dudhwa & Pilibhit in Central Terai: <100 tigers in 1600 km2 ^^^These numbers are disturbing^^^ Such huge areas with such small tiger populations. (04-10-2016, 04:49 PM)Pckts Wrote: Not to derail the thread but wasn't T17's cub from t28 since she originally mated with t25 for a while and was never able to get pregnant until t28 entered the mix then t25 fought her, possibly killed her then the Cubs were lost after that. The documentary followed her for a while. She was seen mating with t28 first and then moved out of her territory to mate with t25. She then had her litter, it was assumed to be t28's since she was last seen mating with him, but no one knows for sure. After a while she just disappeared, along with her cubs, without any trace as to what happened to her.
@Shardul you're correct, I had the two males backwards and I thought the cubs were lost but I was wrong.
here was my original write up on it "Alright, some notes on Tiger's Revenge The story is about the life of T17 (the dominant daughter of Machli, the one who defeated her and took her territory). She was originally trying to have a family with the Star Male but after 2 years of unsuccessful attempts she ventures out of her territory to T25 (the famous male who had to raise his cubs on his own becuase the female died due to natural causes) and she begins to breed with him as well as back with the Star male in her old territory. She then begins to venture between the two territories, she comes across the T25 male again, but this time he is with his cubs, and this is where the famous video of him protecting his cubs is shot, he simply warns her that they are off limits and she gets the hint and goes back to her territory. The monsoon season hits and after it ends the photographer comes back to find out that she has successfully had cubs and is living in the furthest territory of the T25 male and its safe to assume the cubs are his. Her sister takes over her old territory once she has left. This is when drama begins, the Star male is searching for her and he finds her and her cubs and he is not happy. They have a fight since she is forced to protect them, the cubs scatter and she is severly injured in the fight. She searches for her cubs for 2 days until finally she finds them and knowing that its no longer safe to have them there because surely the Star Male will return to finish the job, she moves them towards villagers area and after that she is not seen for a month. The cubs are fed by the forrest guards and are still alive today, unfortunately she has not been seen in over a year and is presumed dead. Whether its from the injuries suffered during the fight or the villagers, the outcome is unknown. A side note, The T25 cubs are tranq'd and moved to another Tiger location that is suffering a low # of females. Very sad, but awesome doc. I highly recommend watching it when you get a chance." and the original doc (04-15-2016, 10:44 PM)Pckts Wrote: Manas in Assam: <30 tigers in 3000 km2 This is the part that worries me the most. The largest reserves are usually the least well protected. Central eastern and north eastern India has some huge swathes of forest, but are among the least protected and managed. No studies have been done on those areas and issues affecting the wildlife there. Manas had the capacity to be another Kaziranga, but militancy put paid to those dreams. Same with the reserves in nearby states like Jharkhand and Chhattisgarh. India needs to decide whether it wants tigers or not. We want development but also want to save nature. We mark reserves to protect animals and then build highways that cut straight through them. The only reason wildlife has managed to survive for so long is because of Indira Gandhi. She was the one who put in place wildlife protection laws and initiated Project tiger in 1972 when the tiger was precariously close to being extinct. Number of tigers and other wildlife rebounded as a whole and, if not for the poaching wave of the 90s, it would have been in a healthy state today. We need someone like her today. Alas, I don't see anyone. (04-15-2016, 08:09 AM)Shardul Wrote: I am not being an optimist at all. An overall higher percentage of sub adults would mean the conditions are excellent, which is far from true. Common problem in India is when a reserve reaches it's carrying capacity of tigers, the sub adults disperse out, lose protection and get killed by humans. The 'source' population remains the same, the extra animals dispersing out have no 'Sink Areas' that can absorb them. Take Ranthambhore for eg, even with the best protection and prey available, it cannot carry 100 tigers. It currently has about 35 and that will remain stable more or less. The resident tigers will keep breeding and the dispersing animals will keep dying if they do not find a suitable habitat outside ranthambhore. Other areas with lesser protection have animals being killed around and some times inside the reserves. Tigers are prolific breeders. Give them enough prey and protection and their population will rebound in no time. If we are debating the number of adult tigers in India ( not actual breeding adults ) I would even accept a higher number in the range of 1500-1600 ( out of 2200 ), now as you know and as tiger scientists continuously state tigresses do not breed and raise cubs when and where the conditions are poor, poor prey base, high human encroachment, excess of infanticidal males..etc. Karanth estimates that over half of the tiger population in India lives in marginal,poor,fragmented, unprotected habitat, so practically half of the adult tigresses may chose not to raise cubs and will not be considered breeding adults ( hence an estimate of below 1000 ), on the other hand we all agree on the resilience and ability to recover of tigers , they are prolific breeders and will quickly maximize their potential ( possibly close to 2000 breeding adults) if we provide them all with enough protection, prey, and space. Sadly this is not the situation for over half of the tigers in India. And you are absolutely right with the absence of dispersal channels that will take sub-adults into establishing territories they will be pushed closer to human habitat and inevitable conflict and death. We can draw hope with some good work connecting some tiger habitat ( naturally or through man-made efforts) in the Terai landscape, the Sunderban, and the Western Ghats but my main concern is the tigers of dry forest in central India, the potential for their sub-adults to become residents is depressingly low. (04-16-2016, 01:14 AM)Shardul Wrote:(04-15-2016, 10:44 PM)Pckts Wrote: Manas in Assam: <30 tigers in 3000 km2 That is 100% true, Indian tigers will be protected and saved by Indian people..villagers, hunters, rangers, and above all policy makers, while India continues its amazing economic growth more and more natural areas will be under pressure, as you said you declare a reserve and then build a highway cutting through it, balancing these two imperatives will take someone of the vision and courage of the late Indira Gandhi. Modhi and other prominent politicians nowadays do not seem to pay enough attention to wild life protection they have other priorities and you can not blame them for it, people elected them to fullfill an agenda and more pressing needs. (04-16-2016, 04:27 AM)Dr Panthera Wrote:(04-15-2016, 08:09 AM)Shardul Wrote: I am not being an optimist at all. An overall higher percentage of sub adults would mean the conditions are excellent, which is far from true. Common problem in India is when a reserve reaches it's carrying capacity of tigers, the sub adults disperse out, lose protection and get killed by humans. The 'source' population remains the same, the extra animals dispersing out have no 'Sink Areas' that can absorb them. Take Ranthambhore for eg, even with the best protection and prey available, it cannot carry 100 tigers. It currently has about 35 and that will remain stable more or less. The resident tigers will keep breeding and the dispersing animals will keep dying if they do not find a suitable habitat outside ranthambhore. Other areas with lesser protection have animals being killed around and some times inside the reserves. Tigers are prolific breeders. Give them enough prey and protection and their population will rebound in no time. In case of Indian tigers, I see a lot of assumptions being made. Outside of a few protected areas, no proper research has been done on the vast majority of it's occupied habitat. The recent census established presence of tigers in hitherto unknown areas, where they were not expected to be. A few months back, a tigress with 3 cubs was found near bhopal city. The cubs were not small, which means she was living there for quit some time. That area is not even a sanctuary, it's just a reserve forest, an area you might call degraded or unsuitable. We have similar examples in other areas. And we cannot assume this to be rare since it came into news only because it happened on the outskirts of a major city. The bulk (2/3rd) of India's tigers are concentrated into protected areas withing a few key landscapes. Only a third reside outside protected areas. You really do need to read up the census report I provided you earlier. While we are in the process of providing low low low figures, why stop at 900? Let's suppose 1/3rd of the <1500 adults are old, another 1/3 are transient. So that would peg the number of adults who are capable of breeding at <500. And since more than half of them are not breeding, that would put the number of breeding adults at <250, closer to 200 then. Which puts the Indian tiger in the IUCN red list. This would do wonders for creating "awareness", not that it's going to stop poachers, but hey, who cares as long as we are all aware. |
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