Aerial single target acuity of harbor seals (Phoca vitulina) for stationary and moving targets of varying contrast.

Harbor seals (Phoca vitulina) need to detect single objects for example when orienting to landmarks or hunting prey. The detection of single objects, described by the single target acuity (STA), cannot be deduced from formerly determined grating acuity (GA) as different mechanisms underlie STA and GA. Thus, we assessed STA for stationary and moving single targets with varying contrast in two harbor seals in a first approach in air.

Single target acuity in the common sunfish (Lepomis gibbosus).

Vision contributes to foraging, territorial and reproductive behavior in sunfish. In these contexts, sunfish need to perceive single targets, such as prey items or body markings from either conspecifics or individuals of other sunfish species, from some distance. We determined the single target acuity of six common sunfish in a behavioral experiment to assess whether the visual abilities of sunfish correspond with behavioral observations or reactive distance measures, and thus assessed the limits of vision for the mentioned behaviors.