Surviving in the wild is tough, as herbivores must watch their backs and carnivores must fend off competition. And in this dog-eat-dog world, canines have developed adaptations that have allowed them to thrive in almost every region on Earth. From Africa's hyenas to Australia's dingoes, from vilified wolves to screaming jackals, canines have been both companion and foe for thousands of years.

No matter if they live in our backyards or in the wild, many canines have the same basic anatomical build. Carnassial teeth (sharp upper premolars and lower molars) make it easier to rip apart flesh -- even allowing some stronger-jawed species to break bones in order to reach the marrow. Their long, tightly bound legs and strong chest muscles allow these creatures to synchronize running and breathing perfectly. This combination creates an animal built to cover far distances, using its stamina to tire out prey. Although it's hard to see these physical adaptations in, for example, your tiny terrier, you can see traces of its wolf ancestry as it chases and thrashes its toys with boundless energy.

Some canines form packs with strict social hierarchies. Usually the leader of the pack doesn't meet such a tragic end like in the 1960s hit song. This canine manages the territorial gang with a whole-is-more-than-the-sum-of-its-parts mentality, allowing the group to kill much larger prey than if each member was on its own.

There's long been a love-hate relationship with canines. Though we treat our dogs as members of the family, we've also decimated coyote and wolf populations. Hunted for their pelts, targeted as carriers of rabies and considered serious threats by ranchers and farmers, canines are trying to adapt to encroaching human populations.

As the call of the wild commands you to join your own pack, defend your territory of knowledge by prowling through HowStuffWorks.