Isolated islands are imaginary evolutionary laboratories where arriving species face new circumstances and change over time, in some cases evolving out previous attributes. Today, some of us hiking the breadth of Isla Santa Catalina in the Sea of Cortez were fortunate to find one of our planet’s iconic evolutionary creations - the rattleless rattlesnake, only found on this one island in the entire world. It is marvelous to ponder this loss of a rattling adaptation once necessary for survival.
Visitors to Galápagos may have seen the flightless cormorant. Flightlessness has derived on many islands (and in many cases, grounded species have gone extinct with man’s arrival). There have also been pigeons, ducks, geese, rails, parrots, ibises, wrens and other flying creatures that have lost their ability to fly. River dolphins living in murky freshwater have gone nearly blind, as have insects that live their entire lives in lava tubes. In some preserved remote places, wildness has disappeared and animals maintain genetic tameness in otherwise potentially predatory situations.
Rattlesnakes developed keratin buttons at the end of their tails to warn off large mammalian predators of the toxic saliva they can deliver; similar snake species that lived without such large animals present never evolved a rattling alert. Rattlesnakes arrived to the fragment of desert that is Santa Catalina Island fully rattling, but over time devolved their threatening maraca shake; without any large predators present, it has evidently become a selective disadvantage to keep rattling.
Catalina is a showcase of evolution, endemism, gigantism and isolation and the island’s preservation is a high priority in Lindblad Expeditions’ Baja Forever! campaign. All nine of Catalina’s reptile species are unique to the island, but without a doubt the rattleless rattlesnake, Crotalus catalinensis, is the most intriguing and emblematic. This creature is a living symbol of the free flow of life on our planet in a time when so many organisms are impacted by the progress and control of man.
With a highflying dolphin encounter in rolling seas we later entered San Jose Channel and tucked in to a protected bay to celebrate Christmas Eve ashore with a dinner barbecue. The near-full moon rose as we celebrated the holidays, as the snakes of Santa Catalina continued their uninterrupted evolutionary traverse through the ages.