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

[peter]

ON THE SIZE OF CAPTIVE AMUR TIGERS - V

V.1 - Introduction

When discussing the dissertation of Weilin (see post 2,574) and the study of Cui et al. (see post 2,575), I said not everything was clear. The reason was the language (both the dissertation and the study are in Chinese). For this reason, I decided to contact 'Betty'. 

A few days ago, the questions I had were answered. In this post, they will we briefly discussed. 

V.2 - Shoulder height

The first question was how the height at the shoulder was measured in the dissertation discussed in post 2,574 (Weilin) and in the study discussed in post 2,575 (Cui et al.). 

Weilin measured the distance from the shoulder blade to the sole of the foot in a straight line. You may remember 8 males of 42 months of age averaged 101,43 cm, whereas 4 males of 54 months of age averaged 98,50 cm. In the largest sample, 25 males of 66 months averaged 96,64 cm. 

According to 'Betty', the tigers in the dissertation published in 2005 and in the tigers in the study published in 2021 were measured in the same way. In spite of that, the results were very different. In the study published in 2021, subadult (2-3 year old) captive male Amur tigers averaged 107,80 cm, whereas adult males (4 years and older) averaged 112,15 cm. If we add the tigers were from the same facility (the Harbin Siberian Tiger Park), the question is why the difference is so pronounced. 

The answer is we don't know. According to 'Betty', the definition used in the study published in 2021 is somewhat unclear. It's also possible those involved in measuring the tigers had little experience and, for this reason, were unable to execute the method described in the protocol. This, however, is just an assumption. 

What is clear, however, is that the (unclear and unsound) method used in the both the dissertation and the study was applied in different ways. This is the reason very different results were produced. If you would conclude methods developed to get to an estimate about the height at the shoulder are bound to produce very flexible, if not unreliable, results, you could be quite close. 

V.3 - Subadult and adult

In post 2,575, I wrote it wasn't easy to understand the differences between Table 2 (averages of subadults and adults) and Figures 3 and 4 (trends). As the information in Figures 3 and 4 is more reliable (the dots, after all, represent all measurements), I concluded Table 2 was somewhat misleading. I assumed it most probably was a result of the decision to distinguish between subadults and adults only. 

According to 'Betty', this assumption is correct. The authors of the study distinguished between subadults (2-3 years of age) and adults (4 years and older) only. The only logical outcome of this decision can be a confusing table. 

V.4 - Conclusions

Like in other large mammals, there are pronounced differences between subadult, young adult and mature tigers. Young adults lose the fat accumulated in the first years of their life during the transition to adulthood. For this reason, they often lose weight in that period. When the transition has been completed, they start growing again. The information collected in the Harbin Siberian Tiger Park strongly suggests growth has different stages. This is the reason one has distinguish (referring to males) between immatures (<2 years of age), subadults (2-3 years of age), young adults (4-5 years of age) and mature animals (6 years and older). Takes a bit of work, but it's the only way to produce accurate tables.   

As to methods developed to get to a reliable estimate of the height at the shoulder. Most of them, as the dissertation and study discussed in posts 2,574 and 2,575 again show, are either unclear or difficult to apply. 

The only reliable method is to measure the actual standing height of adult animals. This is the method V. Mazak used. According to him ('Der Tiger', 1983, pp. 190), adult females (n=5) range between 82-88 cm, whereas adult males (n=7) range between 96-106 cm. Females exceeding 90 cm and males exceeding 110 cm at the shoulder are exceptional. Reply