What is the reproduction rate of the Bengal tigers?

According to the following article:

K. Ullas Karanth, James D. Nichols, N. Samba Kumar, and James E. Hines, 'Assessing Tiger Population Dynamics From Photographic Capture-Recapture Sampling', Ecology 87: 2925-2937.

In Nagarhole, females give birth to three to four cubs per litter every three to four years.

My question is: what would the 'normal' tiger mortality rate be, if we subtracted deaths caused by humans?