Pizzly bears, also known as grolar bears, are hybrid animals resulting from the interbreeding of a polar bear (Ursus maritimus) and a grizzly bear (Ursus arctos). These hybrids have captured scientific and public interest as their presence in the wild has become more documented. Once rare, the increasing overlap in the habitats of polar and grizzly bears, influenced by a changing climate, has led to more frequent encounters between these two distinct species. The first DNA-confirmed wild hybrid was identified in 2006.
Physical Characteristics
Pizzly bears display traits from both parent species, often leaning towards their grizzly heritage. Their fur color is a creamy white base, inherited from the polar bear, but includes brown patches around the eyes, on the paws, or a general grizzled brown appearance, characteristic of a grizzly. Their body structure tends to be more robust than a polar bear’s, yet generally smaller than a polar bear but larger than a grizzly. This intermediate size and stockier build provide a blend of adaptations for both land and potentially icy environments.
A feature inherited from the grizzly parent is the presence of a shoulder hump, though it might be less pronounced in the hybrid. This muscular hump is a hallmark of grizzly bears, providing power for digging and foraging. The head shape of a pizzly bear is also intermediate, appearing rounder and broader than the more elongated skull of a polar bear, reflecting the grizzly’s cranial structure. Their claws are longer and less curved than those of a polar bear, resembling a grizzly’s longer, more effective digging claws. While polar bears have fully furred soles for insulation and grip on ice, pizzly bears have partially hairy soles, another blended trait.
Genetic Factors
The existence of pizzly bears is a direct result of hybridization, where two distinct species interbreed to produce offspring. Both grizzly bears and polar bears belong to the same genus, Ursus, and share a close evolutionary history, having diverged around 500,000 to 600,000 years ago. This genetic similarity, including a compatible number of chromosomes, allows for successful mating and the production of fertile hybrid offspring. First-generation (F1) pizzly bears inherit approximately 50% of their genetic material from each parent species.
The specific combination of genes inherited from the grizzly parent dictates which grizzly-like physical traits are expressed in the hybrid. While some traits, like fur color, can be a blend, others, such as the shoulder hump and claw structure, manifest strongly if the contributing grizzly genes are dominant or expressed. Genetic analyses have confirmed these mixed ancestries, even tracing multiple hybrids back to a single female polar bear mating with grizzly bears. The ability of these hybrids to reproduce, and even backcross with parent species, has implications for the genetic landscape of bear populations in overlapping territories.