Analyses of predation behavior of the desert shrew Notiosorex crawfordi

Abstract

The desert shrew Notiosorex crawfordi is the smallest mammal in the arid and semiarid areas of North America. It displays ecological adaptations that allow it to colonize environments inhospitable for other species in the Order Soricomorpha. Little is known about the natural history of this species; hence, this work reports the characteristics of foraging behavior, prey items, prey size and bite effectiveness on prey items of similar or larger size than these shrews. The behavior in captivity of two individuals of N. crawfordi captured in Baja California Sur was analyzed in glass terrariums, recording the locomotion, posture, food preferences, prey manipulation and bite effectiveness. Preference for prey items collected from the same transects/habitat as the shrews and differing in size and belonging to different groups of Arthropoda was evaluated, revealing a greater preference for scorpions, which were attacked within 1 min of being placed in the terrarium. Observations of foraging behavior of captive desert shrews show that prey items from the different arthropod groups and lizards become paralyzed at the first bite. The behavior displayed by the prey suggested the potential presence of toxins in the saliva of N. crawfordi.

A Comprehensive Multi-Omic Approach Reveals a Relatively Simple Venom in a Diet Generalist, the Northern Short-Tailed Shrew, Blarina brevicauda

“…If dietary breadth is a driver of venom complexity, then one would predict that venomous animals in the Order Eulipotyphla (shrews, moles, hedgehogs, and solenodons) would have extreme complexity of venom toxins. Predatory venom is found in only a few extant eulipotyphlan species ( Dufton 1992 ; Ligabue-Braun 2015 ; Rode-Margono and Nekaris 2015 ; Casewell 2019 ) and may be found in a few other species ( Nussbaum and Maser 1969 ; Folinsbee 2013 ; Camargo and Álvarez-Castañeda 2019) . The selective pressures leading to the evolution of venom in these shrew species is unclear because both venomous and nonvenomous species feed on a diversity of prey items from widely divergent animal groups, including Arthropoda, Annelida, Mollusca, and Chordata (Hamilton 1930; Hamilton 1941 ; Eadie 1952 ).…”

Venom Use in Eulipotyphlans: An Evolutionary and Ecological Approach

“…Similarly, there are some observations suggesting that the masked shrew Sorex cinereus , the American water shrew Sorex palustris , two species of hero shrews ( Scutisorex somereni and S. thori ), the desert shrew Notiosorex crawfordi (and four other species of the genus Notiosorex : N. cockrumi , N. evotis , N. tataticuli , N. villai ), the European mole Talpa europaea [ 17 , 35 , 36 , 75 , 76 , 77 ], and the Japanese water shrew Chimarrogale platycephalus (S. Ohdachi pers. comm.)…”

“…Pearson [ 60 ], however, reported that saliva of this species is not toxic. Observations of foraging behavior of captive N. crawfordi showed that scorpions and lizards are paralyzed with the first bite, perhaps due to the toxins present in this shrew’s saliva [ 77 ]. Notably, the toxicity of saliva from this desert shrew species has also not yet been studied.…”

“…Crocidura canarienis is able to hunt and immobilize Atlantic lizards ( Gallotia atlantica ) [ 74 ], and Notiosorex crawfordi is able to paralyze and subdue some invertebrate and lizard species larger than itself [ 77 ].…”

“…Consistent with this, the weak venom of this species was helpful in overpowering medium-sized prey (earthworms) but not so in overcoming large prey (frogs) [ 17 ]. Additionally, time needed from the first bite by N. crawfordi to the death of its prey was much longer for lizards than for invertebrate prey [ 77 ]. Lastly, nonvenomous S. araneus needed at least twice as much time as N. fodiens to kill large beetles and was not able to overpower the largest ones that were killed and eaten by N. fodiens [ 151 ].…”