Modern weights and measurements on wild tigers

[GuateGojira]

(08-29-2020, 11:14 PM)Balam Wrote: Finally had the time today of combining the weights gathered for wild Sumatran tigers from recent years, the table also includes the hunting records posted by GuateGojira and an average for each category, as well as a combined average. Much like the other tables, it will be continuously updated as new weights come forward. I have also included the table from Slaght et al for point of reference:

*This image is copyright of its original author

*This image is copyright of its original author

*This image is copyright of its original author

*This image is copyright of its original author
Surprisingly the averages for both, the recent weights and Slack et al., match at around 110 kg. Old records present a higher value of 119 kg, and the combined average is close to 113 kg. The range for average weights of Sumatran tigers according to this data is 110 to 119.

On the creation of Averages:

In order to get a good idea of the size of an animal, the collection of information including body mass and length/height is important, altough in modern times this has been abandoned for economic/safety reasons, and that is why the information available is few.

Now, few people gatter this information, like the table above that is from Barlow et al. (2009) that present one of the last efforts to compile information, but the problem is that the table mix captive and wild specimens and some of them are not even in good shape and that is also important. For example, the captive Amur male tiger of 118 kg was obviously not in good shape, the "male" Caspian tiger of 132 kg was not even a male, and the "P. t. corbetti" tigers are not from Indochina but from Malaysia (there is only two or three weights from captive Indochina tigers on record and are not included in this table). This shows that even some of the "official" tables are not free of errors.

The original souce of these figures is the study of Slagth et al. (2005) and is in Russian, however in that table they separated the wild from the captive specimens and that is perfect, although they did not presented ranges, something that Barlow and his team did, so is "half and a half" here. This is the original table, translated with help of Google translator some years ago:

*This image is copyright of its original author

Now, why I bring this information again? Well, the fact is that the use of unhealthy specimens cause serious problems when you try to make an average and the best example is the weights of the wild Amur tigers. As you can see, the figure from Slagth et al. (2005) is of 176.4 kg for males (n=18) and 117.9 kg for females (n=13), please take in count that the samples are not the number of animals but the number of captures, some specimens like the male Pt-20 (or M-20 depending of the source) was captured 3 times with weights ranging from 170 to 205 kg. Now, this average includes at least 3 unhealthy males between 125 and 147 kg, and when you include this figures the average reach this very low figure of about 176 kg, however I gattered the original weights from the old Siberian Tiger Project reports, some new ones from the webpage of the project and the new figures of the Amur Tiger Programme, and I excluded these sick males that were not in good conditions and I got an average figure of 190 kg (n=23), this is a more reliable average figure on the population. Check my old table from 2015, I had not changed yet as no new weight has been reported:

*This image is copyright of its original author

As you can see, it is important to know what we include in the averages and what we don't, as the inclution of unhealthy specimens cause this problem. Now, about the inclution of specimens of of 3 years old of older, we must remember that most of the samples of tigers include specimens of this age, this because that is the age of the sexual maturity, so while some people is not entirely agree with its inclution, there is not to much that we can do on this. Sadly, must of the old hunting records, even those of Brander, Hewett and Cooch Behar, includes young specimens, and based in the low figures of 150 - 170 kg, they were even younger than that, after all some males in the Indian Subcontinent may reach up to 216 kg at the age of 2.5 years old in some cases! The same happens with females, but that is another story.

So, my advice to you is to exclude the specimens that clearly do not show healty specimens, in this case the males of 73 and 74 kg, as not even the captive specimens reach such a low figures. Try to keep a look on this and avoid animals of less than 3 years old and that did not match the ranges stablished. Other example of this is the giant male Sumatran tiger of 185 kg reported by some sources, the figure may be reliable but I did not include it as is bigger than the stablished range for over 20 kg. In this case, we can use those figures as "exceptional" specimens.

This is what we get with the Sumatran tiger figures for males:

*This image is copyright of its original author

It seems that between 117 - 119 kg is the average weight for the males of this population, and c.118 kg is the closer that we can get.

Let's see what new reports can provide us. Reply