Sensationalistic Journalism and Tales of Snakebite: Are
Rattlesnakes Rapidly Evolving More Toxic Venom?
William K. Hayes, PhD; Stephen P. Mackessy, PhD
Department of Earth and Biological Sciences, Loma Linda University, Loma Linda, CA (Dr Hayes); and School of Biological Sciences,
University of Northern Colorado, Greeley, CO (Dr Mackessy).
Recent reports in the lay press have suggested that bites by rattlesnakes in the last several years have
been more severe than those in the past. The explanation, often citing physicians, is that rattlesnakes
are evolving more toxic venom, perhaps in response to anthropogenic causes. We suggest that other
explanations are more parsimonious, including factors dependent on the snake and factors associated
with the bite victim’s response to envenomation. Although bites could become more severe from an
increased proportion of bites from larger or more provoked snakes (ie, more venom injected), the
venom itself evolves much too slowly to explain the severe symptoms occasionally seen. Increased
snakebite severity could also result from a number of demographic changes in the victim proﬁle,
including age and body size, behavior toward the snake (provocation), anatomical site of bite, clothing,
and general health including asthma prevalence and sensitivity to foreign antigens. Clinical manage-
ment of bites also changes perpetually, rendering comparisons of snakebite severity over time tenuous.
Clearly, careful study taking into consideration many factors will be essential to document temporal
changes in snakebite severity or venom toxicity. Presently, no published evidence for these changes
exists. The sensationalistic coverage of these atypical bites and accompanying speculation is highly
misleading and can produce many detrimental results, such as inappropriate fear of the outdoors and
snakes, and distraction from proven snakebite management needs, including a consistent supply of
antivenom, adequate health care, and training. We urge healthcare providers to avoid propagating
misinformation about snakes and snakebites.
: snake, snake envenomation, rattlesnake, venom, Mojave toxin, biochemistry, antivenoms,
mass media, evolution
The media loves a sensational story, and when scientists
and health professionals are quoted, the public will be-
lieve almost anything heard or read. Recently, in 2008,
we witnessed a ﬂurry of media stories perpetuating the
notion that rattlesnakes—particularly those native to
southern California, Arizona, and Colorado (
were rapidly evolving more toxic venom.
ries cited speculation by physicians reporting an unusual
number of severe snakebite cases in recent years. Pub-
lished opinions that snakes are rapidly evolving more
toxic venom are not new. A popularized view, for ex-
ample, was published in an article in
nearly a decade ago.