528 



SCIENCE 



[N. S. Vol. XL. No. 1032 



such encounters, but Kennicott^" is the only 

 writer who has described an encounter in 

 which the shrew was attacked by the mouse. 

 He says: "When attacked by a meadow 

 mouse (Arvicola scalopsoides) , etc. . . ." 

 Shull states, in speaking of short-tailed shrews 

 kept in confinement, that house mice were 

 captured when they entered the shrews' bur- 

 rows, while voles were pursued and cornered 

 above ground, and that most of the killing was 

 done at night. 



While the observations referred to above 

 were regarding house mice (Mus musculus), 

 meadow mice {Microtus pennsylv aniens) and 

 white-footed or deer mice (Peromyscus leuco- 

 pus), the writer found that red-backed mice 

 {Evotomys gapperi) were no exception, for on 

 two occasions a short-tailed shrew which the 

 writer had under observation, overcame and 

 killed a red-back without apparent injury to 

 itself. Morden states that it took about ten 

 minutes for a short-tailed shrew to overcome 

 and kill a meadow mouse larger than itself, 

 and Merriam found his 11.2 gram shrew was 

 half an hour in tiring and half an hour in 

 killing a 17-gram deer mouse. In the en- 

 counter witnessed by the writer, it required 

 twelve minutes for the shrew to kill the mouse 

 after getting its first hold. On another occa- 

 sion the shrew, which weighed 15 grams, 

 captured and killed during the night a red- 

 backed mouse, weighing 29 grams and seemed 

 uninjured after the encounter. 



It is difficult to conceive how a shrew, with 

 its very limited vision (the eyes being prob- 

 ably of service only in distinguishing light 

 from darkness) can capture an uninjured 

 mouse in the freedom of the woods (the box 

 in which the shrew and mice were confined was 

 18 in. X 20 in.) yet this shrew had a syste- 

 matic method of attack, and always opened 

 the skull of its victim in the same general loca- 

 tion, which would seem to indicate that it had 

 had experience in such encounters, or else 

 had acquired the knowledge by heredity, which 

 would also indicate a long series of such 



10 Kennicott, Report of the Oommissioner of 

 Patents for 1857. Agriculture, "The Quadrupeds 

 of Illinois Injurious and Beneficial to the Farmer. ' ' 



battles by its ancestors. An exception to its 

 habitual method of opening the skull was ob- 

 served one day when an adult Norway rat 

 {Epimys norvegicus) freshly killed, was 

 placed in the box. Instead of entering the 

 cranial cavity between the eye and ear, as 

 usual, it opened the throat and worked into the 

 brain through the base of the skull. 



An interesting habit which this shrew 

 exhibited, and which may illustrate one method 

 of capturing mice under natural conditions, 

 was noted as follows : Whenever a live mouse 

 was placed in the box with the shrew, the 

 latter at once secreted itself under some small 

 pile of leaves or moss. In the course of a few 

 minutes the mouse, while exploring its new 

 quarters, would jump on the pile under which 

 the shrew was concealed, whereupon the 

 shrew would spring up and try to get hold of 

 the mouse. This was attempted on several 

 occasions, always, however, without success. 



Animal food in any form seemed acceptable, 

 while only a limited variety of vegetable matter 

 was eaten. It ate grasshoppers (Melanoplus 

 femoratus) and crickets (Oryllus Penn.) with 

 ■avidity; raw beef sparingly, preferring the 

 fat; and small amounts of American cheese. 

 One morning when no other food was at hand, 

 it devoured the abdominal contents of another 

 shrew of the same species, freshly killed. As 

 soon as other food was placed in the box, 

 however, the remains of the dead shrew were 

 at once and permanently deserted, which would 

 indicate that this animal did not become 

 cannibalistic except under stress of circum- 

 stances. In ■ speaking of this habit it may be 

 of interest to quote Merriam's observations on 

 the long-tailed shrew (Sorex personatus), a 

 much smaller animal. He writes, 



I once confined three of them under an ordinary 

 tumbler. Almost immediately they commenced 

 fighting, and in a few minutes one was slaughtered 

 and eaten by the other two. Before night one of 

 these killed and ate its only surviving companion, 

 and its abdomen was much distended by the meal. 

 Hence, in less than eight hours one of these tiny 

 wild beasts had attacked, overcome and ravenously 

 consumed two of its own species, each as large and 

 heavy as itself! 



Another shrew under observation devoured 



