Grasshopper mice are rodents of the genus ''Onychomys'', occurring in North America. They feed on

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...

s and other

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...

Biology

The three species in this genus of New World mice are only distantly related to the common house mouse, ''

Mus musculus Mus or MUS may refer to: Abbreviations * MUS, the NATO country code for Mauritius * MUS, the IATA airport code for Minami Torishima Airport * MUS, abbreviation for the Centre for Modern Urban Studies on Campus The Hague, Leiden University, Net ...

''. They are endemic to the United States and Mexico. The southern grasshopper mouse has around a long body and a tail that is generally long. Its behavior is distinct from other mice. It is a carnivorous rodent, dining on

s (such as grasshoppers),

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wo ...

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

s, centipedes,

scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always en ...

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...

s, and even other mice. It also stalks its prey in the manner of a

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

, sneaking up quietly, and defends its territory by "howling" like a small

wolf The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly un ...

. The grasshopper mouse is known to be immune to various venoms released by its prey (

s, etc.). Grasshopper mice are nocturnal and avoid exposure to bright light.

Ecology

Diet

Grasshopper mice prey on highly venomous arthropods. One example is centipedes that normally kill mice by injecting deadly

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...

through their venomous forcipules. Grasshopper mice move swiftly, while centipedes can only inject their toxin if their prey is held by the centipede's needle-sharp

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...

s. The mouse remains out of reach of the centipede, and attacks it by repeatedly biting through its hard

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

. Each attack on the centipede damages its

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

, until the centipede is paralyzed and the grasshopper mouse can eat it safely. Another example of a venomous arthropod is the bark scorpion (''Centruroides sculpturatus''). The grasshopper mouse survives in the deserts of southwest United States by feeding on the bark scorpion, which are plentiful, due to other resources being less common. Their aggressive nature extends beyond their hunting habits: when held in captivity with other mice, they will often kill and eat those other mice. However, they have a disadvantage when it involves capturing in open areas because of their short legs and wide bodies (which reduces their speed). Fortunately, due to their ability to maneuver well, they are able to move quickly in narrow areas allowing them to capture their prey more efficiently.

Physiology

Pain tolerance

The bark scorpion and the grasshopper mouse have been coevolving with each other so closely that it has affected their physiology. The scorpion uses its stinger to inject toxins into the nervous and muscle tissues which causes disruption in the animal's sensory system. However, as the scorpions stinger evolves to become more toxic, the mice evolve in order to cope with the toxins. Therefore, the grasshopper mice have sensory neurons that have evolved which reject the toxins and prevents pain signals. Researchers now know that the grasshopper mouse barely notices the intensifying sting due to a mutation in the cellular pathway that controls their pain response. Compared to the normal house mouse, the grasshopper mouse has one more amino acid in the protein making up the sodium channel Na+ nav1.8. This change prevents the mouse from processing Na+ currents when injected with the scorpion's venom, which blocks action potential propagation and induces analgesia. By having a better understanding of the grasshopper mouses's cellular mutation, scientists can conduct more research and eventually develop a pain relieving drug.

Communication

''Onychomys'' have six different vocalization types (two

neonatal An infant or baby is the very young offspring of human beings. ''Infant'' (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is a formal or specialised synonym for the common term ''baby''. The terms may also be used to ...

and four adult). They have a wide range of calls that can distinguish them between species, sex, and individuals. For example, the larger mice tend to have deeper voices. When they feel attacked, they will let out a rapid screech/bark.

Species

* Mearns's grasshopper mouse or Chihuahuan grasshopper mouse ''Onychomys arenicola'' *

Northern grasshopper mouse The northern grasshopper mouse (''Onychomys leucogaster'') is a North American carnivorous rodent of the family Cricetidae. It ranges over much of the western part of the continent, from southern Saskatchewan and central Washington to Tamaulipas ...

, ''Onychomys leucogaster'' *

Southern grasshopper mouse The southern grasshopper mouse or scorpion mouse (''Onychomys torridus'') is a species of predatory rodent in the family Cricetidae, native to Mexico and the states of Arizona, California, Nevada, New Mexico, and Utah in the United States. Notab ...

, ''Onychomys torridus''

References

* The Mammals of Texas
Mearns' grasshopper mouse
* The Mammals of Texas

* University of Michigan Animal Diversity Web

{{Authority control Onychomys Mouse, Grasshopper