Body Mass Estimates: Short Faced Bears/Cave Bears

Christiansen (1999b) used several measurements taken in the proximal limb bones to estimate the mean mass of three specimens of A. simus as ca. 770 kg.

Christiansen, P. What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? Annales Zoologici Fennici [Ann. Zool. Fenn.]. Vol. 36, no. 2, pp. 93-102. 1999. (1999).


Personally speaking, I am always interested in sample size specimen details. If we are examining body mass estimates for adult bears, I want to know if we are looking at a young adult or mature adult bear because there's a notable difference in body mass between a bear that is seven years old (a young adult bear) and a bear that is thirteen years old or older (a mature bear) e.g., the Utah Lake Bonville GSFB. Taking a closer look at the GSFB Christiansen (1999b) material, we are told the following specimen details:


The calculated equations were used to predict the body masses of Arctodus simus and Ursus spelaeus. The material used of Arctodus simus consists of 4 humeri and 3 femora (Fig. 1) (at the Field Museum of Natural History in Chicago and the Los Angeles County Museum). None had been sexed, but their general large size would indicate that they were males.


"Cox (1991) and Scott and Cox (1993) showed that some large specimens were present at Rancho La Brea, but that the measurable sample is skewed towards females (the majority of adult specimens) and adolescent males, where long-bone epiphyses were not fused (S. Cox, pers. comm. to Richards, 26 July 1989; Agenbroad and Mead, 1986; Cox, 1991; Scott and Cox, 1993)."

Richards et al. (1996).


Sex biased sampling is a concern in GSFB examination. Anyhow, my examination is preliminary, I plan to follow up if possible on relating data for the FHM GSFB specimens and similarly on the LACM specimens but I am in agreement with Figueirido et al. (2010) in that the Christiansen (1999b) sample size was too small.

Before delving into Suvi Viranta, I think it's important to note that despite the large amount of study and attention given to the Eurasian Cave Bear; collectively speaking, there has been limited body mass estimate studies made and only an additional few analysis based on limb bone (e.g., humerus, femur, etc) examination.

Hello
It seems I read an article a while back by a fella named Figueirido, and Kurten -not sure on the spellings here -that tried to say that the short faced bears weren't really that impressive size wise, they were no where near previous size estimates etc... how could all the previous scientists have been so off in their calculations is my question - if indeed they were in error or is this guy mistaken? just curious to your thoughts on it

I haven't had a chance to again review the material (very busy here) but I feel comfortable with the following posts:

Body Mass Estimation


"Few attempts have been made to estimate the size of the ‘short-faced’ bear. For example, Kurten (1967) used the reconstructed body length and the cross-sectional area of a femoral diaphysis of a large specimen from Hay Springs for calculating its mass as between 470 and 630 kg. Similarly, Nelson and Madsen (1983) obtained an estimate of 620–660 kg for the specimen UVP 015 from Salt Lake County (Northern Utah), based on the diaphyseal area of the femur. Finally, Christiansen (1999b) used several measurements taken in the proximal limb bones to estimate the mean mass of three specimens of A. simus as ca. 770 kg. Unfortunately, all these studies were based on a small number of specimens, which do not reflect the wide intraspecifc body mass range expected in a highly dimorphic species such as A. simus (Kurten, 1967; Cox, 1991). As indicated above, in this study we measured the maximum length and least width of the diaphyseal shaft of each major limb bone in a data set of 58 specimens of the eight species of extant ursids. Log-transformed data were used for calculating least squares bivariate regression functions of body mass on each measurement."


"The fact that one third of the specimens analyzed approached a ton suggests that individuals of this size were more common than previously suspected."


Figueirido, Borja. 2010, Demythologizing Arctodus simus, the ‘Short-Faced’ Long-Legged and Predaceous Bear that Never Was.

shaggygod.proboards.com/index.cgi?board=americaspleistocene&action=display&thread=329&page=1


and.....


Figueirido: 957 kg (same thread, see reply #5).



Lastly.......






Above: They are the largest GSFB's (mature specimens) found on both of the America's. Photo of the Kansas specimen (it's a cast replica) has not been published until now/here.