VENOMOUS ANIMALS
OF THE SOUTHWEST
WHY TALK ABOUT VENOMOUS
ANIMALS?
SO THAT YOU’RE NEITHER OVERLY
WORRIED…
NOR OVERLY…
WELL, YOU KNOW
Most rattlesnake bite
victims are young men
(18-28 yrs old) who are
bitten while handling or
provoking the snake.
How to avoid being bitten or stung
• Never handle venomous animals
• Never place your hands or feet anywhere you
can’t see (and haven’t checked). For example:
– Never step into or over bushes
– Never reach up onto a rock or ledge
– Always pick up rocks, wood, etc. carefully,
making sure not to put fingers under the
rock/wood, always lift it so that the
rock/wood is between you and the potential
animal, and always check underneath. It is
best to use a tool to lift a rock/wood.
POISONOUS VS VENOMOUS?
• Poisonous animals possess toxins.
– For example, this Sonoran Desert Toad
produces and secretes toxins from glands
on its skin. The toad’s toxins are able to
kill dogs that bite the toad!
e.g., Parotoid Gland
POISONOUS VS VENOMOUS?
• Venomous animals inject
their toxins.
– For example, this
rattlesnake produces
toxins in modified
salivary glands then
injects toxins through
hollow fangs.
THE CHARACTERS:
MILDLY VENOMOUS ANIMALS
• Non-life-threatening except by
anaphylactic shock in those that are
allergic.
• Wasps, bees, ants, most spiders, most
scorpions, etc.
THE CHARACTERS:
DANGEROUSLY VENOMOUS ANIMALS
• Life-threatening. Need to seek medical
attention.
• Bark scorpion, black widow, brown spider,
gila monster, coral snake, rattlesnakes.
TYPES OF VENOM
• Hemolytic: affects circulatory
system (“hemo” = blood) by
destroying blood cells and vessels.
Symptoms include severe pain,
swelling, discoloration, and local
tissue death. Shock can occur.
Example: most rattlesnakes.
Rattlesnake bite picture source
http://www.venomous.com/snake/armpic.jpg
TYPES OF VENOM
• Neurotoxic: affects nervous system
(“neuro”). Symptoms may include local
pain, headache, lethargy, paralysis
and occasionally death by circulatory
arrest or respiratory paralysis.
Usually no swelling, discoloration, or
tissue death. Examples include Black
Widow, Scorpions, and Coral Snake.
TYPES OF VENOM
• Other:
– Gila Monster toxin
causes pain.
– Brown (“Recluse”)
Spider toxin
destroys proteins,
thus tissues.
Likely brown spider bite
WHY BE VENOMOUS?
1. Subdue Prey: allows predator to reduce
chance of injury and to eat larger prey.
2. Defense: protects animal from predators
and other potential threats.
3. Digest Food: venom is modified saliva,
produced by modified salivary glands.
Most contain compounds that aid in
digestion (thought to be the “original use”
of venom).
WHY NOT BE VENOMOUS?
1. Takes Special Equipment: requires
glands to produce toxins and often
specialized apparatus for injecting
venom (teeth, modified ovipositor,
etc.).
2. Takes Energy and Materials: toxins
are expensive to produce.
WAYS TO AVOID WASTING TOXIN
• Match amount of venom to prey: use
less for smaller prey, use more for
prey that can get away easier (e.g.,
birds).
AVOID USING TOXIN
• Hide (use cryptic coloration): camouflage.
• Warn (use aposematic coloration): bright,
memorable colors and/or patterns.
AVOID USING TOXIN
• Retreat
ONE MORE WAY TO AVOID
USING TOXIN
• Don’t produce toxins at all – be a Fake!
– Batesian Mimics just pretend to be dangerous
or inedible. Thus potential predators avoid
them, but it doesn’t cost them.
Some useful terms
• Nocturnal: active at night (e.g.,
scorpions)
• Diurnal: active during daylight hours
(e.g., gila monsters)
• Crepuscular: active during dawn and
dusk (e.g., deer tend to be most
active around sunrise and sunset)
DANGEROUSLY VENOMOUS
ANIMALS:
ARACHNIDS (8-legged)
• bark scorpion: of 30 AZ species of scorpion,
only the bark scorpion sting is considered
life-threatening. Identified by long, thin
pincers. Climbs, is nocturnal, and is
neurotoxic.
Bark scorpion
Stripe-tailed scorpion
Compare
pincer
shapes
DANGEROUSLY VENOMOUS ANIMALS:
ARACHNIDS (8-legged)
• “black widow”: Nocturnal, makes
strong, messy web. Neurotoxic.
DANGEROUSLY VENOMOUS ANIMALS:
ARACHNIDS (8-legged)
• “brown spider”: thin, spindly spider with
three pairs of eyes in semicircle (difficult to
see). May have violin-shaped marking on
cephalothorax (“head”). Bite causes tissue
damage.
Compare to Wolf Spider which is not deadly
marking
DANGEROUSLY VENOMOUS ANIMALS:
REPTILES
• Gila monster: only other known venomous lizard
in the world is Mexican beaded lizard (in Mexico).
• Diurnal, but spends 98% of time in burrow; peak
activity in spring when hunting nestlings/eggs. Has
“leaky” skin. Venom for defense (pain) only.
DANGEROUSLY VENOMOUS ANIMALS:
REPTILES
• coral snake: member of cobra family.
Has highly toxic venom but small
fangs and mouth so difficult to bite
humans. Nocturnal. Neurotoxic.
Identified by the phrase: red
and yellow kill a fellow (notice
how red band touches yellow
bands); versus red and black
friend of Jack (non-dangerous
snakes have red touching
black).
DANGEROUSLY VENOMOUS ANIMALS:
REPTILES
• Rattlesnakes: 11 species (17
subspecies) of rattlesnakes in
Arizona
TRUE OR FALSE?
• You can tell the age of a rattlesnake by
counting the segments of its rattle.
• Baby rattlesnakes are more dangerous.
• Rattlesnakes must be coiled to strike.
• Rattlesnakes always rattle before striking
• Rattlesnake eggs are good eating
• Rattlesnake bites are always fatal
• All False
Source: AGFD
RATTLESNAKE SENSE ORGANS
Eyes: to see
Nostrils to
smell
Pit Organ to
sense heat
Body to feel ground vibrations
Cont >>
RATTLESNAKE
SENSE ORGANS
Jacobson’s Organ
to augment smell
by analyzing
chemicals brought
to it by the tongue
which picks up the
chemicals from the
air and ground.