The Moo-derer

Kelly’s Field Notes

Common Name: Grasshopper Mouse

Order:  Rodentia

Family: Cricetidae

Genera: Onychomys

Species: There are three species of grasshopper mouse!

• Mearns's grasshopper mouse or Chihuahuan grasshopper mouse (Onychomys arenicola) - found from the southwestern U.S. to Mexico.

• Northern grasshopper mouse (Onychomys leucogaster) -found in southwest Canada to Mexico.

• Southern grasshopper mouse (Onychomys torridus) - found in California, Nevada, Utah,  and northeastern Mexico.

Description: 

Grasshopper mice are small mostly nocturnal New World mice with short tails compared to other mouse species. Grasshopper mice are about 15 cm (6 in) from nose to tail and weigh 42.1 g (1.5 oz.). They are that classic mouse brown fur with a white belly and pink limbs and tail.

Grasshopper mice are found in short-grass prairies, shrub deserts, and desert grasslands.

Life Cycle: 

Grasshopper mice come together to mate, otherwise they avoid each other (meetings often lead to fights and one killing the other). Adults have a special call used to attract mates. Females give birth to a litter of up to six pups (gestation time is from 32 to 47 days). The young are evicted by their mother after about 20 days, ready to go off on their own. Grasshopper mice can live a total of about five years in captivity, but many wild mice only live for a few months. This is partially due to their willingness to attack nearly anything within range even at a very young age.

Grasshopper mice do not create their own burrows, they instead evict other animals from theirs! They are also highly aggressive and will “howl” to defend their territory. The howl is a high pitched, long screech not dissimilar to a tea kettle whistle. Grasshopper mice are sometimes called werewolf mice because of their howl. They are also voracious predators, eating animals sometimes much larger than themselves and often venomous. They have even been recorded killing and eating birds! Interestingly, their jaws are stronger than similarly sized mice and their stomachs are adapted to deal with sharp exoskeletons (digestive glands are protected in a separate pouch). Additionally, grasshopper mice have the longer large intestine of a carnivore. Their claws are also longer to hold onto smooth arthropod prey.

Venom Resistance:

Grasshopper mice live on a diet of dangerous and sometimes venomous creatures. Some they are resistant to and others they are not. The mice often feed on centipedes but are not resistant to their venom. Instead, they rely on agility to avoid the centipede’s sting. The mouse then bites the centipede’s back, damaging its nervous system, until it is paralyzed and harmless.

Grasshopper mice are resistant to Arizona bark scorpion venom! Bark scorpion venom is a neurotoxin, meaning it affects the nervous system. The mouse, however, has an interesting adaptation to get around this. Scorpion venom is a mix of salts and proteins.Sodium is required by cells to maintain fluid balance, it allows electrical signals to cross the cell membrane, and is essential for nerve function - a sodium based neurotoxin is “smart” because the cell membrane “wants” to allow it in. Disrupting these sodium ion gates is a common mechanism in various biological toxins. The toxins are built to bind to the sodium and potassium ion channels within the muscle and nerve tissues. This “excites” the tissues, disrupting normal function and causing pain. A disruption in function, in this case, could affect lung function. 

In grasshopper mice, their sodium ion channels have a mutation (one extra amino acid in the protein that makes their sodium channel) that causes pain to essentially turn off when the bark scorpion’s neurotoxin binds with it. This special sodium channel also prevents nerve excitement because it prevents the processing of the sodium in the neurotoxin. 

Super Powers:

• Venom Resistance

• Claws

• Howl - grasshopper mice have several calls, two specific to young and four specific to adults. They will also bark/squeak when threatened.

• Stalking/Sneak - grasshopper mice often stalk their prey, more like cats than mice.

• Dodging - grasshopper mice are slow, but agile! They can dodge, weave, and avoid attacks from predators and dangerous prey.

• Vicious - these little guys and gals are fighters! They will attack nearly anything they can get their claws on.

• Teeth - sharp little rodent teeth.

Grasshopper Mouse Videos:

The Grasshopper Mouse Is a Killer Howling Rodent | Nat Geo Wild - https://www.youtube.com/watch?v=1K9mO5QzOIQ

Howling Mouse | Nat Geo Wild - https://www.youtube.com/watch?v=izizsAodOCk

References:

“A Species Account of the Northern Grasshopper Mouse (Onychomys Leucogaster) | Mammals of Texas | Natural Science Research Laboratory | TTU.” Ttu.edu, 2017, www.depts.ttu.edu/nsrl/mammals-of-texas-online-edition/Accounts_Rodentia/Onychomys_leucogaster.php. Accessed 23 Nov. 2024.

Gilchrist, John, Baldomero M. Olivera, and Frank Bosmans. "Animal toxins influence voltage-gated sodium channel function." Voltage Gated Sodium Channels (2014): 203-229.

Langley, William M. "Evolutionary changes in the predatory attack of carnivorous rodents: A comparative analysis emphasizing grasshopper mice (Onychomys spp.)." Journal of Comparative Psychology 135.1 (2021): 114.

‌“Meet the Southern Grasshopper Mouse, the Killer Mouse That Howls at the Moon When It Strikes.” Discoverwildlife.com, 2024, www.discoverwildlife.com/animal-facts/mammals/southern-grasshopper-mouse-the-mouse-that-howls-at-the-moon. Accessed 23 Nov. 2024.

Rowe, Ashlee H., and Matthew P. Rowe. “Predatory Grasshopper Mice.” Current Biology, vol. 25, no. 21, Nov. 2015, pp. R1023–R1026, https://doi.org/10.1016/j.cub.2015.07.054.