  We show that "Malthusian flocks" -- i.e., coherently moving collections of
self-propelled entities (such as living creatures) which are being "born" and
"dying" during their motion -- belong to a new universality class in spatial
dimensions $d>2$. We calculate the universal exponents and scaling laws of this
new universality class to $O(\epsilon)$ in a $d=4-\epsilon$ expansion, and find
these are different from the "canonical" exponents previously conjectured to
hold for "immortal" flocks (i.e., those without birth and death) and shown to
hold for incompressible flocks with spatial dimensions in the range of $2 < d
\leq 4$. We also obtain a universal amplitude ratio relating the damping of
transverse and longitudinal velocity and density fluctuations in these systems.
Furthermore, we find a universal separatrix in real (${\bf r}$) space between
two regions in which the equal time density correlation $\langle\delta\rho({\bf
r}, t)\delta\rho(0, t)\rangle$ has opposite signs. Our expansion should be
quite accurate in $d=3$, allowing precise quantitative comparisons between our
theory, simulations, and experiments.
