218 



Department of Conservation of Louisiana 



A specimen being secured, it was identified as Mus 

 norvegicus, the Norway or common house rat. It was a 

 female and contained 16 embryos. 



It is quite probable that the damage done was from 

 the beaks of grackles and blackbirds. It has been found 

 that the common meadow mouse (Microtus) does consider- 

 able damage by nibbling on the skins of dead trapped musk- 

 rats, but the ordinary house rat has never been considered 

 an enemy until Stark's report was received. 



Observation in Louisiana indicates the Louisiana musk- 

 rat averages four young to a litter from the following em- 

 bryonic count: 



19 females, 



67 females, 



168 females, 



650 females, 



141 females, 



9 females, 



1 female, 



1 embryo 



2 embryos 



3 embryos 



4 embryos 



5 embryos 



6 embryos 



7 embryos 



1058 Averaged 3.846% 



This count, which covers several years, has been made 

 in the so-called highly productive seasons, but it is only fair 

 to point out that the majority of examples cited are from 

 examinations made in the low-production years, and it is 

 noteworthy that the count since 1923-24 and 1924-25 has 

 been decidedly low, and scarcely averaged three to a litter. 

 That this low production a litter may be directly attrib- 

 utable to the drought years of 1924 and 1925 does not 

 appear unlikely, but it certainly does prove that this is a 

 phase that needs investigation ; if it does indicate that the 

 years of plenty mean happy and contented animals with 

 large families, then we will have progressed on our search 

 to the reason for mammalian periodic fluctuations. 



Longevity 



Investigating the habits of any mammal, particularly a 

 fur animal, calls forth many questions from those engaged 

 in trapping for a livelihood. One of the principal questions 

 that has been asked from one end of the state to the other 

 is: "How long does a muskrat live?" 



