Modern weights and measurements on wild tigers

[Dr Panthera]

(12-20-2016, 11:41 AM)peter Wrote: In Russia, young males disperse between 18-24 months of age. In India, they seem to disperse between 24-30 months. This although conditions in India are better. The most likely reason is small reserves, no buffer zones and intense competition. For this reason, young males can be as heavy as mature animals.    

My advice is to distinguish between adolescents (2-3), young adults (4-5), prime males (6-10) and old tigers (11 and over). In skulls, the distinction between age classes often is well visible.

When you have information about individuals, try to contact those in the know to check what you have (Copters proved it can be done). Maybe they can tell you a bit more about fluctuations (collars often are replaced) and it's possible they also have info about total length. When you have weights, try to find out if the tigers were empty or not when they were weighed. Also try to find out a bit more about the scales used.

In order to get to an assessment, we need large samples. The larger the sample, the more reliable the table. My guess is there are 500-800 adult male tigers in India today. Read a bit about sample size, statistics and conclusions.          

When done, also try to get to a conclusion on reliability (referring to the sources used). I'd distinguish between low, medium and high.

And then there's regions. Based on old records, there could be pronounced differences between the elevated Himalayas (the Terai, Nepal and Bhutan), the alluvial floodplains in the northeast (like Kazirangha), the wetlands in the Ganges and Bhramaputra delta (the Sunderbans), the highlands of central and central-eastern India (like Kanha), the plateau of southern India (the Deccan) and southwestern India (the western Ghats).   

The reason to publish tables in WildFact is a lack of data in peer-reviewed documents. In some documents, the data are unreliable because weights were adjusted. Sizewise, peer-reviewed not always has meaning. The reason is only few biologists are interested in size (a lack of interest can result in a lack of knowledge). This is the reason old data are used so often. Also remember most samples are small, which could result in bias.   

Our aim is to collect data and enable readers to get to an opinion. What we don't want, is tables based on newspaper reports only. This is a very real danger. For example. I've read a number of reports about the large male who was moved from Ranthambore after he had killed four humans. In nearly each of them, the weight mentioned was different. He wasn't the only one.

I know it's quite a job, but it's the only way to get to decent tables. Good luck.

Excellent points Peter and if I may elaborate a little:

* In most of the Indian subcontinent ( with the exception of the Sundarbans ) tigers live in small isolated reserves surrounded by thousands of people, the sub-adult tigers are forced to spend an additional 6-12 months with their mothers during their fastest growth phases and attain almost adult size.

* Most of the readings in this thread are newspaper articles and Facebook posts , no scientific value and highly dubious...the perfect round numbers, the absence of equipment description or stomach content adjustment , hardly any mention to other readings commonly taken for sedated /dead animals ( length, tail length, shoulder height, hind foot length...etc) , having said that some have more details and verification from the biologist/veterinarian involved and seem reliable.

* Like most big mammals tigers show great size variation I have seen records of 70 kg males and others of almost 4 times that number, 65 kg females and an alleged 200 kg record, geographic, environmental, and genetic factors and even the individual may show major fluctuation throughout its life time and through different physiological states most available measurements of small samples are for healthy, prime-aged adults who are territory holders since they are the easiest to locate...territorial males are only 5-10% of the total population and less than a third of all males. So a large sample ( at least fifty ) would reduce erroneous conclusions.

* Biologist are interested in size but to a certain degree...the Oxford University team compiled great data about Hwange lions, Smuts measured almost 400 lions between Kruger and Kalahari, the Serengeti Lion Project from Frankfurt zoo and the joint Russian-American research team measured many Amur tigers. Veterinarian sources have more data about size than biological sources and their expertise are greatly needed since even an accomplished biologist like Dr Karanth had overestimated the weight of tigers on at least three occasions leading to fatal doses of the sedative and needless deaths of tigers.
Sedatives used in tranquilizing wild cats (e.g. midazolam , ketamine) have very narrow therapeutic index and a dose for an estimated 250 kg tiger would kill an actual 180 kg tiger, such unfortunate instances as well as the fear of accidents of sedated animals (e.g. drowning, falls) or the sedated animal getting attacked by conspecifics (especially in lions) or rival predators limits the attempts to tranquilize and measure valuable animals.

* Biologists accept 400-450 lbs ( roughly 180-200 kg) as  the size for an average Amur and non-Sundarban Bengal tiger and 450-500 lbs ( roughly 200-225 kg ) for a large individual these numbers were determined through a mixture of field measurements, zoo records, and credible hunting records, biologists are more interested in female weights since 3/4 of the female weight is what is used in determining biomass . Science strives to conserve tigers , their size is needed to determine their feeding ecology needs based on 5.5 kg/day/FEQ ( female equivalent) to ensure that sufficient prey base is present and protected.

* It amazes me how people are fascinated with the subject of size and less so with the conservation of tigers...whether the average tiger is 100kg, 150kg, 200kg, or 250 kg is immaterial when it remains endangered to critically endangered and very likely to vanish in less than a century. Reply