White-tailed Ptarmigan

White-tailed ptarmigans produce alarm calls that vary with predator type—a referential alarm system in an alpine ground-nesting bird. Different calls for aerial versus terrestrial predators trigger appropriate escape responses. This parallel to prairie dog and vervet monkey systems demonstrates that predator-specific calling evolves across diverse taxa facing multiple predator types.

Ground-nesting creates intense predation pressure. Ptarmigan eggs and chicks are vulnerable to both mammalian and avian predators. The predator diversity combined with ground exposure may select for sophisticated alarm systems—you can't escape hawks and foxes the same way.

Cryptic coloration complements alarm calling. Ptarmigans are famous for camouflage that changes with seasons—white in winter, mottled in summer. The alarm call system adds active defense to passive camouflage. Multiple defense layers provide redundancy when one layer fails.

Breeding males call more than females. Like many alarm systems, calling serves dual functions—genuine warning plus status advertisement. Males who call frequently may demonstrate quality to females while also providing protection benefits to mates and offspring.

For organizations, ptarmigans illustrate that defense requires multiple layers. Perimeter security (camouflage) plus active monitoring (alarm calls) plus appropriate response protocols create robust protection.