Blood from a stone: Do the trace metals of sperm whale coproliths reveal a contribution from squid haemolymph?

Background: Ambergris is a coprolith produced by some sperm whales (∼1 %). It has been hypothesised that the metals in ambergris derive from the haemolymph of squid in the whale diet (mainly copper). However, few data exist. We report analysis of 10 trace metals in each of 50 ambergris samples by inductively coupled plasma-mass spectrometry. Main Findings: Acid digests of the samples contained ∼5 to >6880 µg g⁻¹ air-dried weight total metals; mainly of iron (present in ∼90 % of samples, 38), copper (∼95 % of samples, 40), zinc (93 % of samples, 39) and cadmium (∼95 % of samples, 40). Conclusions: We suggest the variable and sometimes high concentrations of iron may reflect traces of haemoglobin or myoglobin from the whales. There may be other sources. The other major metals (Zn, Cu, Cd) are those also reported in several squid species. The distributions are unlike those of squid haemolymph alone, reportedly dominated by copper, or those of the sperm whale (e.g., skin), dominated by zinc.