WordPress Numeric Pagination with Query String [duplicate]

It looks like the paged variable isn’t being added to the query arguments. This should work:

$paged = ( get_query_var('paged') ) ? get_query_var( 'paged' ) : 1;
$args = array(
    'post_type' => 'animals', 
    'posts_per_page' => 4, 
    'category' => $queryString,
    'paged' => $paged
);
$wp_query = new WP_Query( $args );

Also, as a note, $wp_query is a WordPress global variable. It would be safer to use a different name like $my_query, $custom_query, $steve, etc.