Answer: We can expect that the correlation coefficient will increase once the outlier is removed.
The Pearson's correlation coefficient is known to be sensitive to outliers. Outliers can inflate or deflate the correlation coefficient to the extent that it can lead to wrong conclusions.
An outlier that is mostly consistent with the trend will inflate the correlation coefficient; while an outlier that is not consistent with the trend will decrease the correlation coefficient.
In this case the weight and tail lengths of one mouse is inconsistent with the trend. When this data is removed from the sample, we can expect the value of r to increase.