extremely high tides, which completely submerge most vegetation and 

 thus force mice from cover, are encountered only in winter. The mice 

 are in considerable danger of drowning and avian predation at this 

 time. During these high tides, mice hide in what emergent vegetation 

 remains, swimming freely on the water surface as little as possible. 

 However, swimming and diving abilities are well developed. Evidence 

 presented shows that Microtus usually remain on their home ranges dur- 

 ing and after these very high tides, and it is concluded that only the 

 rare, combined effects of wind, rain, and the several factors that pro- 

 duce high tides will displace a population, or reduce its size, to any 

 great extent, (A. A.) 



Keywords: salt marshes, mice populations, San Francisco Bay 



V-C-11 ^ 



Newman, J.R. 1970. Energy flow of a secondary consumer ( Sorex sinuosus ) 



in a salt marsh community. Ph.D. Thesis. University of California, 



Davis. 113 pp. (Diss. Abstr. 32:883-B) 



The purpose of this thesis was to test the importance of the effects 

 of certain abiotic and biotic factors on energy flow through higher 

 consumers. In particular, the aim was to describe the energy flow 

 through the salt marsh shrew, Sorex sinuosus . 



The error of estimate attributable to certain abiotic and biotic 

 factors ranged from one percent because of metabolic age differences 

 of the population to 65 percent because of seasonal differences in 

 the heat energy of respiration. The major biotic and abiotic factors 

 affecting the energy flow through this secondary consumer are metabolic 

 sexual differences, seasonal and daily metabolic rhythms, activity, 

 digestive efficiency, ambient temperature changes, and prey avail- 

 ability. 



Shrew densities varied with season and types of habitat. In optimum 

 habitat areas, densities of 45 shrews per acre are found. The energy 

 flow through the shrew population is estimated to be 105,615 kcal per 

 acre per year. Because of low digestive efficiency, the energy intake 

 is estimated to be from 132,000 to 210,000 kcal per acre per year. In 

 terms of impact on the salt marsh community, the shrew population is 

 the second largest energy consumer of the salt marsh small mammals. 

 Potentially the energy consumption of shrews is greater than a number 

 of primary consumers. Although shrews are not apparently limited by 

 food supply, they could have a significant effect on the density and 

 diversity of the invertebrate fauna. (A. A.) 



Keywords: energy flow, salt marshes, secondary consumers, salt marsh 

 shrew 



246 



