/// Called on [/mob/living/Initialize(mapload)], for the mob to register to relevant signals.
/mob/living/proc/register_init_signals()
	RegisterSignals(src, list(SIGNAL_ADDTRAIT(TRAIT_UNDENSE), SIGNAL_REMOVETRAIT(TRAIT_UNDENSE)), PROC_REF(undense_changed))

/// Called when [TRAIT_UNDENSE] is gained or lost
/mob/living/proc/undense_changed(datum/source)
	SIGNAL_HANDLER
	update_density()