In a companion paper, we introduced raising operator series called Catalanimals. Among them are Schur Catalanimals, which represent Schur functions inside copies Λ(X m,n ) ⊂ E of the algebra of symmetric functions embedded in the elliptic Hall algebra E of Burban and Schiffmann.Here we obtain a combinatorial formula for symmetric functions given by a class of Catalanimals that includes the Schur Catalanimals. Our formula is expressed as a weighted sum of LLT polynomials, with terms indexed by configurations of nested lattice paths called nests, having endpoints and bounding constraints controlled by data called a den.Applied to Schur Catalanimals for the alphabets X m,1 with n = 1, our 'nests in a den' formula proves the combinatorial formula conjectured by Loehr and Warrington for ∇ m s µ as a weighted sum of LLT polynomials indexed by systems of nested Dyck paths. When n is arbitrary, our formula establishes an (m, n) version of the Loehr-Warrington conjecture.In the case where each nest consists of a single lattice path, the nests in a den formula reduces to our previous shuffle theorem for paths under any line. Both this and the (m, n) Loehr-Warrington formula generalize the (km, kn) shuffle theorem proven by Carlsson and Mellit (for n = 1) and Mellit. Our formula here unifies these two generalizations.