INCREASE OR DECREASE DETERMINED. 91 



DETERMINATION OF INCREASE OR DECREASE OF SEALS. 



Page 93 of The Case. 



The compact order in which the breeding seals arrange themselves 

 upon the "rookeries" upon their arrival in the 

 spring, completely filling the ground first taken H. N. Clark, p. 159. 

 before spreading over adjoining space, enables one 



to see at a glance, as the season advances, whether, if he remembers 

 the land marks to which they filled out in former years, they have 

 grown more or less numerous. 



Yet their habits are so well defined and unvarying that it is an easy 

 matter to determine whether they increase or de- 

 crease from year to year, because they always s. H. Mclntyre, p. 48. 

 occupy the same portions of certain beaches, and 

 simply expand or contract the boundaries of the rookeries as they 

 become more or less numerous. 



The rookeries are covered by the breeding seals in a very compact 

 and regular manner. There is no evidence of 

 crowding or bunching in one place, or scattering j, m. Morton, p. 67. 

 in another, and apparently no spaces within their 



limits, suitable for occupancy, which are not covered. It is evident 

 from this systematic arrangement and distribution that any expansion 

 or contraction which may take place of the rookery boundaries must- 

 show a corresponding increase or diminution of their population; and 

 further, that as the rookeries enlarge or diminish, so in a like ratio will 

 the general body of the seal life be affected. By careful and intel- 

 ligent study, then, of the breeding grounds, any material changes 

 which may take place from year to year in the numerical condition of 

 the seal life on the two islands may be determined. 



But it is impossible to determine by close observation from year to 

 year whether the seals are increasing or decreas- 

 ing, because the seals crowd together in the same j. h. Moulton, p. 71. 

 manner, whether there are a few or a great num- 

 ber, and as they increase the rookeries necessarily extend. 



I do not pretend to be able to say how many seals there are, or ever 

 were on tbe rookeries; nor do I believe anybody 

 else can tell; for. the rookeries are so broken and j. c. Redpath, p. 151. 

 filled with rocks it is impossible to estimate the 



number of seals upon them with any approach to accuracy. The lines 

 of expansion and contraction are plain enough, and can be seen and 

 understood by the whole community. 



I believe that the increase and decrease of seal life can be certainly 

 told from accurate measurements of the breeding 

 grounds, because the seals herd together as closely w. B. Taylor, p. 176. 

 as possible, whether there are few or many of 

 them. 



The density of the seal population on the rookeries is the same each 

 season; an increase of seal life simply extends the 

 space occupied by the rookeries. By observing s. M. Waslbum, p. 155. 

 each year the extent of ground covered with 

 breeding seals and comparing it one year with another an observer can 



