ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)

[GuateGojira]

(10-10-2023, 08:00 AM)peter Wrote: GUATE

We met well before Wildfact was created. Furthermore, you've been here from day one. I consider you a friend and that will never change, meaning I accept you're 'The One who greets with Fire'. Part of the deal. 

Also part of the deal is friends talk straight. What i was saying (referring to my previous post) is it's unfair, and pointless, if a senior member, and one with a reputation at that, targets a younger member for no reason. You, of all people, should know how it feels when someone targets you. I'm referring to the exchanges in the period 'WaveRiders' was here. He was the new kid on the block and delivered quality, but I didn't like the way he went for our mods and you in particular. I told him, but he ignored the advice and continued until a decision was made. You know I'll defend a friend, that is. You also know I dislike members using their experience and reputation to act in a similar way as Wave did. 

Apex, to be sure, didn't contact me to complain. I acted because I want those who post in this thread to cooperate. They were invited because they have what is needed: quality (not only referring to access to good information). You're one of them, but so, in my opinion, is Apex. Both of you have different qualities. Next time you see something you don't like, contact me. And when you start a discussion, focus on arguments only. I don't mind the occasional touch of logic, but stay away from what we see every bloody day all over the net (arrogance, insults and all the rest of it). And when you feel the fire burning, just count to ten. 

Back to the issue at hand. I'm, to be more precise, referring to the fifth proposal.   

About the correlation between 'heel width' and weight in wild Amur tigers 

You said there's a difference between a print left in, say, soft snow and an actual measurement of the paw 'in the flesh' in that a print is always larger than an actual measurement of the pad 'in the flesh'. Meaning a print isn't accurate and, for that reason, unreliable. 

You're, of course, right. In spite of that, the remark is irrelevant. 

Field biologists and rangers, as you know, not often have the opportunity to measure a wild tiger these days. When you study a rare species, one thing you want to avoid at all costs is risks. Every capture has risks. For this reason, biologists and rangers often have no option but to use indirect information to get to a guesstimate. Like a print. Although a print isn't accurate, it isn't about accuracy. It's about the correlation between the print and the size (weight) of the animal that left it.  

The question is if a print enables a ranger to get to the information he's after. If he's following a tiger that might have to be captured, his aim is to find out a bit more about the specifics (gender, age, size and condition).    

He knows there's a quite strong correlation between the width of the pad of the front paw ('heel width') and the weight of the tiger that left the print. The 'heel width' of adult females ranges between 8,5-10,0 cm, whereas healthy adult males range between 10,5-13,0 cm, at times a bit more. He also knows adult Amur tigresses range between 100-130 kg (up to 140) these days. Male Amur tigers (using confirmed weights only) range between 140-212 kg (140 for 'Tikhon', a very old male, and 212 for 'Luk', a young adult captured in the southern part of Primorye), but a large male in his prime might be considerably heavier (referring to recent information about the weight of wild male Amur tigers captured in northeastern China).  

An adult healthy Amur tigress leaving a print with a 'heel width' of 9,5-10,0 cm is large. Chances are a pad of that size corresponds with a tigress of 120-130 kg, possibly a bit more. A healthy adult male Amur tiger leaving a print with a heel width of 12,0 cm is larger than average. Note I added 'healthy' every time, because the information I have strongly suggests the correlation between heel width and weight is affected by age, health and conditions.  

One of the tables in the document published in 2005 (Table 7.3) has detailed information about the size of 13 wild adult male Amur tigers and 10 adult wild females. It's, again, not superfluous to underline tigers Table 7.3 has a few young adult males (3-4 years of age). The average heel width of 10 'adult' tigresses captured in the period 1992-2004 was 9,2 cm (range 8,5-10,0), whereas the average heel width of 12 males captured in the same period was 11,4 cm (range 10,5-12,8). All tigers and tigresses were captured in the Sichote-Alin Biosphere Reserve and its environs:

*This image is copyright of its original author

*This image is copyright of its original author 
We know (referring to another table in the document published in 2005) tigresses averaged 117,9 kg, whereas males averaged 176,4 kg (389 pounds). Does this mean an adult wild Amur tigress with a heel width of 9,2 cm is 117,9 kg and an adult wild male Amur tiger with a heel width of 11,4 cm is 176,4 kg? In the Sichote-Alin Biosphere Reserve, at the level of averages, the answer (in that period of time) is affirmative. At the level of individuals, the answer is no. Like always, it depends. 

My proposal is to have a closer look at the correlation between 'heel width' and weight in average-sized wild males. Table 7.3 says males captured in the Sichote-Alin Biosphere Reserve and it's environs in the period 1992-2004 averaged 176,4 kg (range 125-200) and 11,4 cm in heel width (range 10,5-12,8). The heel width, to be complete, was measured 'in the flesh' (all males were captured, measured and weighed). 

I do not, as you seem to assume, doubt the accuracy of the information, but wonder if the table is representative. There are two reasons. The first is young adult males were included. The second is the table has no information about tigers in the Khabarovsky Krai and northeastern China. My 'hypothesis' for now is the inclusion of young adult males in particular had an effect on the averages (referring to heel width and weight). Is there a tool to get to a kind of assessment? A tool like, say, 'heel width'?   

The answer is affirmative. I found 3 tables that have the information needed and selected 6 wild males at least 5 years of age. The average heel width of these 6 was 11,56 cm (range 11,5-11,8). Anything known about the health of these males? 

The answer is four had health problems. Significant problems, I may add. 

The first male (168 kg and 12-13 years of age) had his front paw nearly torn off by a brown bear (...), whereas the second (a 10-year old male of 192 kg) was killed by another male. He had a pathology of the paw bone and was no match for the other tiger. The third male (185 kg, but with a relative low fat index) had been injured by a bullet. He was shot when he attacked a group of hunters. The fourth male (171 kg, but with a relative low fat index) was shot with a permit because he had attacked domestic animals. Male five (189 kg at 6,5-7,5 years of age) and male six (a young adult of 207 kg), healthwise, seemed to have a clean sheet. I, by the way, added the young adult ('Banzai'), because the information I found suggests he could have been a bit older than 4 when he was captured. 

In spite of the (significant) problems, these 6 males averaged 185,3 kg (range 168-207), whereas the males in the table published in 2005 averaged 176,4 kg. Not a big difference, but it is if the health problems of the 6 males I selected are considered. Meaning age, weightwise, seems to be as important as health, if not more so. Also meaning the inclusion of young adults (referring to Table 7.3) had an effect on the averages.      

Anyhow. The information available suggests heel width is a quite decent indicator of the weight of a wild tiger, especially if there's additional information. More often than not, it will enable experienced woodsmen and biologists to get to a decent guesstimate. 

Hi peter, nice to see you starting the discussion, based in data and in your educated form. Is good to read you as allways. It is a good balada, but now is my turn with a passionated tango!

Correlation between 'heel width' and weight in wild Amur tigers
It may be a surprise to all the people that has not read the document of Kerley et al. (2005) that the scientists of the Siberian Tiger Project did managed to stablish correlations between several body measurements and check how reliable are to get the weight of the Amur tigers, however, before to disclose the results, let me show you what I got.

Based in the sample of the individual tigers from Dr Linda Kerley and team, I got a sample of 12 sexually mature males (in other words, "adults" of over 3 years old) with both body mass and front heel wide. From these sample, 3 are reported with healty problems, and from these at least one was in good shape in its first capture. The next image shows the sample together with its name, weight and heel wide. 

*This image is copyright of its original author

Table 1 shows the figures as are show by Dr Kerley and team in the monograph, the result provide the lowest correlation (r2=0.1559). Table 2 shows the specimens with the maximum weights recorded (take in coun that male "Aleksei" was not weighed in its dfirst capture, but estimated between 160-170 kg, depending of the source, so I use a figure of 165 kg for the calculation, even then the correlation is just slightly better but still unreliable (r2=0.1859). Table 3 include only the healthy specimens but use the average weights, the final result is a little higher correlation (r2=0.2435) but is still under the 0.5 necesary for reliability. Table 4 use the healthy specimens with using the highest weights recorded for them, the correlation is the best (r2=0.27) but did not reached the 0.5. In conclution, using this sample we found that there is no correlation between the weight and the heel wide of the male tigers, altough we must remember that the figures of the heel measurements are also averages of several measurements, which may affect the result. 

Now, I will include the specimens reported by Igor Nikolaev and Victor G. Yudin in the document "Conflict between man and tiger in the Russian Far East" of 1993. There is the paper where you got the extra males that you mentioned before and the sample of this study says that based in the analisys of 75 tiger deaths, 40% of the tigers were killed in or near settlements, 32% were killed by poachers and the death of 28% of the animals were not human related. In few words, these animals were mostly problematic animals and based in the description most of them were injured or in bad state. This is the table that I furnished and that include only the male specimens that were actually weighed:

*This image is copyright of its original author

Those in black were clasified as "reliable" as they health status was not that bad, with high fat index most of them, all of them over 3 years old and few patologies. Those in blue were clasified as "problematic" based in the fact that the fat index was middle to low and the injures reported were more serious. Finally those in red were clasified as disable as they were in bad shape with low to starving status most of them and all had serious injures and were very ill. Please take in count that this clasification is just from my part so it is not necesary the final form to clasify the specimens. It is interesting to note that one of the biggest heels (12.0 cm) belonged to a male of only 145 kg! No fat index was reported but probaly it was in very bad conditions.

*This image is copyright of its original author

Using these males and those from the Siberian Tiger Project and The Amur Tiger Programme, the Table 1 use all the specimens and the correlation is very poor (r2=0.1039), the lowest of all, taking in count that big paw specimens were in very bad conditions. Table 2 used only the the healhty specimens from the STP/TATP and the "reliable" specimens from Nikolaev & Yudin (1993), and the correlation is among the highest (r2=0.2386) of this group. Finally Table 3 use the healthy specimens of the STP/TATP and the "reliable" and "problematic" specimens from Nikolaev & Yudin (1993), and provide the highest correlation of all (r2=0.2913). At the end no combination provided a correlation over 0.5.

So, using all these specimens we could conclude that the heel wide is not a good predictor for body mass in male Amur tigers, but which was the conclution of the scientists of the Siberian Tiger Project in 2005? Incredible they sample of 11 adult males, they got many more measurements and here are the results from the table 7.5 in Kerley et al. (2005):

Original in Russian:

*This image is copyright of its original author

Translate to English:

*This image is copyright of its original author

As we can see, based in 19 measurements from captured and death animals the wide of the front heel resulted with a very high correlation of r2= 0.55 (n=19), but the highes one is wide of the front paw with a correlation of r2=0.65 (n=20). This means that the relation is significative and that a calculation of weight based in the wide of the paw (not the heel) is regularly reliable, however is still not enough estatistically speaking as is too close of the 0.5 which means that any calculation based in the size of the paw is like a 50/50 bet and must be taked with caution. Now check that for females the wide of the front heel is the most correlated with r2=0.55. However, ths is nothing agains the measurements tha actually shows very high correlation, like is the chest circunference in males (r2=0.95) and females (r2=0.86). That is why in figure 7.3 of the same document they develop an equation with the chest girth, and not with the paw/heel wide. In conclution, while the wide of the fron paw in males, and the wide of the front heel in females, shows significan correlation (over 0.5) is still not enought to get a reliable form to get the weight of the animal that created it, like we see in the samples that we got from living animals.

Now, you mention that Biologist use the paw/heel to get the weight of the animals right? Actually that is not correct, they only use these measurements primarly to get the sex, age and possible health status of the animal in order to made the population census, now the weight is something that they don't do, and is only they own personal guesses, educated and maybe usefull, but only guesses. If you can get the book "The Ecology of the Amur Tiger based on Long-Term Winter Observations in 1970-1973 in the Western Sector fo the Central Sikhote-Alin Mountains" from Anatoliy Grigorievitch Yudakov and Igor Georgievitch Nikolaev, translation from 2004, there you can see in Chapter 1 that how and why they use the paw prints, and in ANY momento they mention anything about weight, and there is a lot of data about tracks in that chapter. In fact this fragment is very interesting:

*This image is copyright of its original author

Now you see my point? These are not my words, but the words from the real scientist that studied the tigers in the field.


Check this from Heptner & Sludskii (1992):

*This image is copyright of its original author

As you can see, they only say that big males are over 200 kg, but that is all, only rogue estimations and at the end, as the previous book said, paw prints are mostly used to estimate sex, age and health status. You don't see professional Biologist stating that a tiger with a big heel weight "this" or "that", even the picture of the "giant" monster tiger of the Khabarovsk region do not mention any weight, only say that is "big" and big is a wide form to describe an specimen. In fact, I have several pictures of "huge" tigers captured by the STP but as we know, none of them surpassed the 205 kg. So that is why I say that using a single measurement (or a picture with no point of comparison) is impossible to get an accurate estimation of the size/weight of an animal. 

Next post I will continue with the other parts of your post. Reply