Introduction

This report will serve to analyse population dynamics and the rates of euthanasia for shelter dogs and cats across multiple shelters within Las Angeles within the 2014/2015 financial year. It is extremely important to analyse and enhance communication of such data as currently the dispossession of animals from shelters is ‘largely based on voluntary surveys with low response rates—make it difficult to estimate the population from which the euthanized animals derive’ (Bartlett, 2005). Furthermore, poor estimation of euthanasia rates can have large impact on the underestimation of the companion animal problem across America and other countries. This study aims to identify a difference between dog and cat euthanasia rates. Our Null Hypothesis would determine that on the average, the numbers of dogs and cats being euthanised is equal (population mean cats = population mean dogs). Comparatively, our Alternative Hypothesis would reveal that on the average, the number of dogs and cats being euthanised is not equal (population mean cats ≠ population mean dogs). This is a two-sided alternative hypothesis.

Box Plots

Figure1. Comparative boxplot of euthanised shelter cats/dogs in Los Angeles during the 2014/2015 financial year

Figure1. Comparative boxplot of euthanised shelter cats/dogs in Los Angeles during the 2014/2015 financial year


Analysis of box plots

When analysing the box plots it can be identified that the respective median for the number of euthanised dogs lie outside the interquartile range of euthansied cats (Figure1). Such analysis suggests there will be a significant difference between the two populations. When identifying the spread of the two box plots it is evident that the rate of euthanasia for cats has a wider distribution (1,806 - Summary cats)and more scattered data whilst slightly positively skewed (Figure 1). In comparison the rate of euthanasia for dogs has a significantly more narrow and concise distribution (492 after excluding the outlier - Summary dogs) with a significantly positively skewed data when including the outlier and normal skew when excluding the outlier . Both variables being analysed are independent, the euthanasia rates of dogs does not effect the euthanasia rates of cats.

Summary Cats

##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##   388.0   934.2  1215.0  1319.8  1853.5  2194.0

Summary Dogs

##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##   131.0   300.0   518.5   646.7   617.8  1834.0

Hypothesis testing

Figure2. Combined boxplot of euthanised shelter cats and dogs in Los Angeles during the 2014/2015 financial year

Figure2. Combined boxplot of euthanised shelter cats and dogs in Los Angeles during the 2014/2015 financial year 



## 
##  One Sample t-test
## 
## data:  Euthenised$EuthenisedCats - Euthenised$EuthenisedDogs
## t = 4.0545, df = 5, p-value = 0.009782
## alternative hypothesis: true mean is not equal to 0
## 95 percent confidence interval:
##   246.3761 1099.9573
## sample estimates:
## mean of x 
##  673.1667

P value = 0.009782

Conclusion

The P value < 0.05 (Figure3)therefore we succeed in rejecting the null hypothesis, confirming our alternative hypothesis and concluding that there is strong evidence to suggest a difference in the rate of euthanasia of dogs versus cats. In this instance our alternative hypothesis was that the rates of cat euthanasia is significantly higher than the rate of dog euthanasia within Los Angeles shelters.

Similar research findings

Bartlett, 2005 analyses population dynamics and the rates of euthanasia for shelter cats and dogs in Michigan, demonstrating the importance of regular participation in shelter discharge data in estimating and combating companion animal overpopulation. Bartlett, 2005 utilised high response surveys as well as the ‘Pet Shops, Dog Pounds, and Animal Shelters Act, 1969’ to obtain annual data from Michigan shelters regarding the dispossession of their animals. The study found that in 2003 40% of dogs and 57% of cats were discharged by Michigan shelters through euthanasia. Such findings in comparison to thus study, suggests that the difference in euthanasia ratio of shelter dogs and cats has continued the same trajectory for numerous years.

Bartlett, P, Bartlett, A, Walshaw, S, & Halstead, A 2005 ‘Rates of Euthenasia and Adoption for Dogs and Cats in Michigan Animal Shelters’, Journal of Applied Animal Welfare Science, vol. 8, no. 2, pp. 97-100. https://doi.org/10.1207/s15327604jaws0802_2