5 Ailuropodinae

Figure 5:2: Skulls of Panda Bears & Panda Coons

(A) Sichere 1944; (B) Thenius 1974; Panda-coon Thenius 1979

Figure 5.3. Giant panda bear (Ailuropoda melanoleuca)

The true significance of a panda’s “baby face” is not a happy disposition, but the extraordinarily powerful jaw muscles and teeth necessary to eat bamboo -- not just the juicy bamboo shoots we humans enjoy in oriental meals, but bamboo stems so large and tough that they are used as construction materials throughout the orient. I have seen scaffolding more than 20 stories tall built of bamboo poles in place of the steel used in North America. In fact, bamboo stems are so light and flexible, yet tough, that you can think of them as a natural equivalent of the carbon-fiber poles we now use for fishing.
It’s hard to imagine any animal other than termites eating something that woody. Yet, it’s the primary food of panda bears and of a raccoon-like animal known as a bamboo-coon or red panda (Figure 5:4).

Figure 5:4 Bamboo-coon (red panda) Ailurus fulgens.

Figure 5:5. Bamboo stands. Two species.

Figure 5:6. Bamboo stem. Piece approximately 2’ long and 2” in diameter.

When a panda eats, a length of bamboo stem is held in one or both hands. Sinking its canines into the stem, a panda rips off a strip of the wood in roughly the same way you might rip meat off a barbequed beef rib. (Figure 5:7).

Both pandas and panda-coons have heavy-duty canines and incisors for biting off chunks of stem, as well flat molars and huge jaw muscles for grinding the wood (Figures 5:8-5:9)

Figure 5.7. Eating bamboo. Strips are bitten off then chewed thoroughly before being swallowed.

Figure 5.8. Panda skull. (Photo of a display at the San Diego Zoo.) Skull shape of the pygmy panda was similar, suggesting that they too foraged on bamboo.

Figure 5:9. Close-up of teeth on right lower jaw. C=canine, P=premolar, M = molar. Canines are use for biting food or enemies. Premolars are used for slicing food. Molars are used for grinding food. As in all bears, the first premolar is normally missing. In the panda, however, unlike other bears, the 2nd, 3rd and 4th premolars are large and sharp.

Figure 5:10. Dentition of grizzly/brown and black bears.

Figure 5.11 Right hands of a panda (above) and a brown bear (below). Note the mobile pseudo-thumb on the inside of the wrist of the panda. In all living bear species, there is also an immobile bone on the outside of the wrist. Both wrist bones “oppose” the 5 fingers and thereby assist in gripping bamboo stems and tree limbs. (Photo of a display at the San Diego Zoo.)

Both pandas and panda-coons have heavy-duty canines and incisors for biting off chunks of stem, as well flat molars and huge jaw muscles for grinding the wood (Figures 5:8-5:9) Having a locally-abundant food source almost to themselves was undoubtedly a temporary boon for pandas. But dependence on this single food prevented pandas from emigrating across land without bamboo and thus from spreading to other parts of Eurasia, much less to other continents. No panda fossil has ever been found outside China (Figure 5:1). Tight dependence on bamboo also leaves panda populations vulnerable to extinction during those rare years when edible bamboo is unavailable. Even when edible bamboo is scarce, there may be a wealth of herbs, forbs, fruits, nuts and animal foods which are eaten by other species of bears, and which pandas can digest. Yet, these foods are largely ignored. Those factors, coupled with human impacts, have driven pandas to the brink of extinction. But for intensive conservation efforts by the Chinese people and outside assistance from dedicated individuals like George Schaller, the giant panda might no longer exist in the wild.

Two species of panda bear are known, the extinct pygmy (Ailuropoda microta) which was probably around 3 ft long, and the 5-ft-long giant (A. melanoleuca) that still survives (

Fig. 5:1). Their fossil remains, dating back to the early Pleistocene, have been found in eastern China at least as far north as Choukoutien and as far south as Burma. (Woodward 1915, Chu & Long 1983) (

Fig. 5:2). Now, by contrast, their range is reduced to six small areas totaling about 29,500 km2 on the eastern edge of the Tibetan plateau (Schaller et al. 1985).

Scarcity of fossils is only one basis for the century-old controversy over whether the giant panda is really a bear or a "raccoon" (procyonid). Despite the gross anatomical similarity of giant panda to bears, there are more subtle anatomical and behavioral differences (Morris & Morris 1966; Ewer 1973). The panda bear has distinctive reproductive organs and an unusual scent gland, with which it exhibits unique marking behavior (Morris & Morris 1966). The panda's head and forepaws are specialized for its diet of primarily bamboo pith, a very coarse food. The broad zygomatic arches and high sagittal crest provide attachments for long, massive jaw muscles. (Sicher 1944). Unlike Ursinae and Tremarctinae, the panda bear retains the second and third premolars and sometimes the first. These premolars and the molars are highly developed for crushing and grinding food, being even broader than those of other bears--which, including the extinct Pleistocene Ursinae, have lost all but the last premolar. (Ewer 1973). Among other ursids, modification of the last premolar and the molars for herbivory reached their zenith in the cave bears of Europe and North America and in spectacled bear (Kurte'n 1976). Having observed captive or wild bears of all species, Herrero (pers. comm.), concluded that behavior of even the spectacled bear is more similar to Ursinae than either of those subfamilies are to panda. There are, however, sound reasons why some biologists suspect that the giant panda is more closely related to the red panda (Ailurus fulgens), an animal similar to an American raccoon (Procyon lotor). Ewer (1973) was particularly impressed by differences from typical bears in how pandas hold food (bamboo), whereas both giant panda and red panda hold it the same way. Their teeth (premolars and molars), skull and skull muscles (massiveness) are similarly adapted for feeding on bamboo. Thus, like Morris & Morris (1966) and numerous other biologists before them, Ewer (1973) concluded that giant panda and red panda are more closely related to one another than to other animals. This view has been bolstered by recent evidence on haemoglobin structure. The minimum mutation distance, in amino acid units, is 7 between the two pandas, 11 between giant panda and polar bear, and 18 between red panda and raccoon (Tagle et al. 1986).

Nevertheless, evidence that giant pandas are really bears and red pandas procyonids is overwhelming. This evidence involves anatomical details of the paws, skull, skull musculature, and teeth, as well as karyotypic and biochemical data.

There are numerous other anatomical reasons for concluding that the giant panda is a bear and the red panda a procyonid whose dependence on bamboo caused them to evolve convergently (Davis 1964). This analysis of comparative anatomy by Davis is considered without peer in our century (Gould 1986). Davis showed that the massive skull and jaw muscles and enlarged molars and premolars by both pandas are essentially what one would expect for adaptation to feeding on coarse vegetation--traits comparable to those of the spectacled bear, Florida cave bear, and European cave bear (see Kurten 1976). Furthermore, the red panda's dentition is only roughly similar to that of a panda bear; and the red panda lacks a pseudo-thumb, although the radial sesamoid is somewhat enlarged (Ewer 1973).

The convergence hypothesis is further supported by karyotypic and biochemical evidence. The 3 ursid subfamilies differ markedly in diploid chromosome number (74 Ursinae; 52 Tremarctos; 42 panda bear). But, 36 for red panda is comparable to the normal procyonid number of 38 (Wurster 1969; Thenius 1979). Reviewing data on genetics, biochemistry (Leone & Wiens 1956; Sarich 1973), morphology, and behavior, Thenius (1979:Fig. 7) concluded that the giant panda is a true bear and the red panda a procyonid, as argued by Pocock (1921). That is strongly bolstered by the additional studies on karyotype, DNA hybridization, isozyme genetic distance, and immunological distance by O'Brien et al. (1985). Mayr (1986) dismisses the haemoglobin evidence of giant panda-red panda linkage as just another phenotypic trait in which evolution of giant and red pandas converged due to living in the same habitat, eating mainly the same food. But how haemoglobin similarities between giant and red pandas would have been particularly adaptive to their location and diet remains unclear. Studies might fruitfully be done on the hemoglobins of other mammals in that region or which eat bamboo. In particular, the Asian black bear should be tested.

Mayr's hypothesis on convergent evolution of haemoglobin structure is unconfirmed. But rest of the evidence strongly favors the view that the giant panda is a true bear, assigned to subfamily Ailuropodinae.

* * *

In this chapter, we have examined what is known about bear phylogeny, that is about which bears are ancestors or descendants of one another. We have also considered the geographic distribution of each species. Let us now examine in more detail the environmental factors which may have shaped ursid evolution and geographic radiation, and the ways in which bears met these challenges.

Chapter 5. AILUROPODINAE

Figure 5:12. Current Distribution of Panda Bears