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POPULATION DYNAMICS, FOOD HABITS, AND ECONOMIC IMPORTANCE OF HOUSE RAT (Rattus rattus) IN VILLAGES AND FARM HOUSES OF CENTRAL PUNJAB (PAKISTAN)

Hassan, Muhammad Mushtaq-Ul (1993) POPULATION DYNAMICS, FOOD HABITS, AND ECONOMIC IMPORTANCE OF HOUSE RAT (Rattus rattus) IN VILLAGES AND FARM HOUSES OF CENTRAL PUNJAB (PAKISTAN). PhD thesis, University of Agriculture, Faisalabad.

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Abstract

SPECIES COMPOSITION During the period extending from July, 1987 through June, 1990, a total of 1965 specimens of small mammals -1422 from village structures viz., village houses, village shops, and flour mills (collectively designated as village complex), and 543 from farm houses was snap trapped. Four species of small mammals, namely Rattus rattus, Mus musculus, Tatera indica, and Suncus murinus were represented in the samples from these two habitats. In village complex samples, R.rattus was predominant. In the yearly samples, the proportion of This species varied from 73% (in 1988-89) to 76% (in 1989-90). The proportions of M.musculus, T.indica, and S.murinus in the yearly samples varied from 15% (in 1987-88) to 21% (in 1988-89), 0% (in 1988-89) to 2% (in 1987-88), and from 5% (in 1989-90) to 7% (in 1987-88), respectively. In the three years seasonally combined data, the proportion of R.rattus was some what better in the spring (77%) and summer (76%) as compared to that in the fall (74%) and winter (71%) M.musculus was better represented in the winter (24%) and spring (22% samples than in summer (19%) and fall (7%) samples. T.indica was represented in the fall (3%) and winter (2%) samples only. S.myrinus was best represented in the fall (16%), poorly in the summer (5%) and winter (3%) samples, whereas in the spring accounted for only 1% the total catch. In the farm houses too R.rattus was predominant. In the yearly samples, its proportion ranged from 54% (in 1987-88) to 73% (in 1989-90). The proportion of M.musculus varied significantly from 3% (in 1989-90) to 9% (in 1988-89), of T.indica from 15% (in 1988-89) to 26% (in 1987-88) and of S.murinus from 2% in 1989-90) to 12% (in 1987-88). In the three years seasonally Combined samples, the proportion of R.rattus varied from 41% (in summer) to 88% (in spring), of M.musculus varied from 4% (in winter) to 10% (in fall), of T.indica from 0% in spring) to 47'% (in summer), and of S.murinus from 2% (in summer) to 21% (in fall). The proportions of these species in the pooled data were 64%, 7%, 22%, and respectively. In the yearly samples of the pooled data (of village complex and houses), the proportion of R.rattus varied from 69% (in 1987-88) to 75% (in 1989-90), of M.musculus from 13% (in 1987-88) to 18% (in 1988-89), of T.indica from (in 1988-89) to 9% (in 1987-88), and of S.murinus from 4% (in 1989-90) to 8% in 1987-88). In the three years' seasonally combined data from the two habitats, the proportion of R.rattus varied from 64% (in summer) to 79% (in spring), of M.musculus from 7% (in fall) to 20% (in spring), of T.indica from 0% (in spring) to 16% (in summer), and of S.murinus from 2% (in spring) to 17% (in fall). In the three years combined data of the two habitats the respective proportions were 72%, 15%, 7%, and 7%, respectively. Although the village complex and farm houses harboured the same four species of small mammals, yet the latter habitat showed better evenness with respect to abundance of the species. POPULATION SIZE The trapping data permitted estimation of the population size of R.rattus by regression of daily captures on cumulative captures, and that of the small, mammals (including the house rats) by regression of daily captures on cumulative captures as well as by change-in-ratio method. It was estimated that an average village structure harboured 7 house rats in 1987-88, 5 in 1988-89, and 3 in 1989- 90: overall average being 5. An average farm house supported 6 rats in 1987-88, in 1988-89, and 5 in 1989-90; overall average being 5. An average structure, irrespective of the fact whether it was located in a village or in the fields (farm house), harboured 7 rats in 1987-88, 5 in 1988-89 and 3 in 1989-90; the average being 5 rats. An average meter square space of a village complex structure accommodated .40 rats in 1987-88, .30 in 1988-89, and .18 in 1989-90; the average for the three years being .31 rats. An average one meter square space of the farm houses supported .10 rats in 1987-88, .08 in 1988-89, and .06 in 1989-90; the average being .09 rats. The number of rats per villager ranged from 1.06 (in 1987-88) to .48 (in 1989-90): the average for the three years was 78. An average structure of the village complex harboured 10 (estimated by removal regression method) to 12 (estimated by change-in-ratio method) specimens of small mammals in 1987-88. The estimates obtained by the two methods for 1988-89 as well as for 1989-90 were the same, that is, 7 and 4, respectively. The three years average obtained by the two methods was the same, that is, 7. An average farm house supported 12 (estimated by removal regression) to 14 specimens of small mammals (estimated by change-in-ratio method) in 1987-88, 7 to 8 in 1988-89, and 6 in 1989-90; the average for the three years being 8 and 9. The pooled village complex and farm house data indicated that an average rural structure Supported 10 (estimated by removal regression) to 12(estimated by change-in-ratio method) small mammals in 1987-88, 7 to 8 in 1988-89, and 5 in 1989-90; the average being 7 to 8. The per meter square density of small mammals (estimated by removal regression and change-in-ratio method) averaged .27 and .30 and the number of rats per person averaged 1.0 and 1.11. REPRODUCTION The 50% points of sexual maturity with respect to body weight (BW), and head and body length (HBL) were located at 73 g and 146 mm for males and at 74 g and 143 mm for the females of village house rats, at 77 g and 152 mm for males and at 71 g and 145 mm for females of village shop rats, at 72 g and 151 mm for the males and at 67 g and 137 mm for the females of the flour mill rats, and at 82 g and 150 mm for the males and 78 g and 146 mm for the females of the farm house rats. Sexual dimorphism in the BW and HBL of the adult rats was statistically significant in the case of the village house (of village complex) rats only. The proportion of adult breeding males in the village complex varied during the three years of the study from 82% (in 1989-90) to 92% (in 1987-88); the average being 88%. In the farm house rats, the proportion of breeding males ranged from 88% (in 1987-88) to 95% (in 1988-89): the average for the three years was 90%. In the lumped data (of village complex and farm houses), the proportion of breeding male rats varied from 84% (in 1989-90) to 91% (in 1987-88). Seasonal variations in the proportion of breeding males were generally not statistically significant. In village complex rats, prevalence of pregnancy ranged from 20% (in 1987-88) to 30% (in 1988-89); the average being 25%. In the farm house rats, prevalence of pregnancy varied from 14% (in 1989-90) to 26% (in 1988-89); the average was 20%. In the combined sample of village complex and farm houses, the prevalence of pregnancy varied between 20% (in 1987-88) and 29% (in 1988-89); the average being 24%. These yearly variations were statistically non-significant. In the village complex rats, mean annual embryonic litter size varied from 7. 16+0.38 (S.E.) in 1988-89 to 5.86+0.45 (S.E.) in 1989-90; the average being 6.68+.24 (S.E.). These variations in the annual estimates of the litter size were statistically significant. In the farm houses, mean annual litter size ranged from 8.10+.56 (S.E.) in 1988-89 to 7.22+.62 (S.E.) in 1987-88; the average was 7.67+0.66 (S.E.). In the combined data of village complex and farm houses, mean annual litter size varied from 7.32+0.35 (S.E.) in 1988-89 to 6.30+0.42 (S.E.) in 1989-90; the average being 6.86+0.21 (S.E.). The near-term embryonic litter size (assessed from the crown-rump length of the embryos) averaged 6.07+0.35 (S.E.) for the village complex rats, and 6.00+0.47 (S.E.) for the farm house rats; the combined estimate for the two habitats was 5.94+0.99 (S.E.). The ratio of the two sexes in the immature segment of the village complex sample did not Deviate significantly from the theoretical 1:1. In the adults, however, the ratio was skewed in favor of females, but this skewness was statistically significant in the 1987-88 and in the three years combined data. In the farm house rats, the disparity in the ratio of the two sexes was much stronger especially in the case of the adult rats in which females predominated in all the yearly samples at statistically significant levels. Recruitment of young rats into the population continued round the year. In the village complex rats, the average proportion of young varied from 37% (in 1989-90) to 43% (in 1987-88); the average being 40%. In the farm house rats, proportion of young rats ranged from 38% (in 1987-88 and 1989-90) to 44% (in 1988-89); the average being 40%. In the combined sample (of village complex and houses) the proportion of young varied between 38% (in 1989-90) to 42% (in 1987-88); the average being 40%. These variations were statistically significant only in the farm house samples. Monthly recruitment of immature rats was significantly correlated with the prevalence of pregnancy both in the village complex and farm house rat populations. FOOD HABITS The village house rats were found to consume, at least, 12 food items. Among these wheat (67.4%) together with rice (6.4%) and maize (5.5%), accounted for 79.3% of the total diet of the rat. Oilseeds (4.5%), fodders (3.6%), weeds (2.7%), sugarcane (2.7%), sorghum (0.9%), and gram (0.9%) jointly contributed 15.3% to the rats diet, whereas 1.8% was due to animal matter and 1.8% due to unknown items. The village shop rats exploited 11 food items. Wheat (45.3%), oils (11.8%), rice (7.6%), pulses (6.7%), unknown items (5.9%), and sorghum (5.0%) jointly constituted 82.3% of the total dry weight of the stomach contents. The remaining 17.7% was due to gram (4.2%), animal matter (4.2%), maize (3.4%), fodders (3.4%), and sugarcane (2.5%). The flour mill rats consumed 10 food items. Wheat accounted for 70.2% of the rats diet while the remaining 29.8% was due to rice (5.8%), sugarcane (4.4%), gram (4.4%), maize (3.6%), fodders (3.6%), animal matter (2.9%), Sorghum (2.2%), oilseeds (2.2%), and unknown items (0.7%). The farm house rats exploited 12% items of food. Wheat (53.4%), fodders (8.9%), sugarcane (8.0%), rice (6.3%), oilseeds (5.4%), and gram (5.4%) jointly constituted 87.4% of the total diet. The remaining 12.6% was due to weeds (3.6 maize (2.7%), sorghum (2.7%), animal matter (1.8%), pulses (0.9%), and unknown items (0.9%). The house rat of the rural central Punjab mainly fed on seeds of plants which were supplemented with some greens. The greens predominated in the diet of the farm house rats. Animal matter, on the whole, constituted only 1.8% of the rats diet. It was computed that from an average house about 29.5 kg and from an average village about 12,394 kg of cereals was lost to the rat every year.

Item Type:Thesis (PhD)
Uncontrolled Keywords:House Rat (Rattus rattus), Rattus Rattus, Mus musculus, Tatera Indica, and Suncus Murinus
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Paleo-zoology(c1.10)
ID Code:299
Deposited By:Mr Ghulam Murtaza
Deposited On:18 Jun 2006
Last Modified:04 Oct 2007 21:00

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