Boobies that were experimentally food-deprived for forty-eight hours experienced a decrease in foot brightness due to a reduction in the amount of lipids and lipoproteins that are used to absorb and transport carotenoids.
Angsa batu yang secara eksperimental kekurangan makanan selama empat puluh delapan jam mengalami penurunan kecerahan di kaki karena pengurangan jumlah lipid dan lipoprotein yang digunakan untuk menyerap dan mengangkut karotenoid.