Shelters and other hidden zones
Hidden zones and Entry zones
You can define a shelter or any zone where the animal is out of view as a Hidden zone. After you have defined a hidden zone, you must define at least one Entry zone for that hidden zone. The entry zone is used to determine whether the animal has entered or left the hidden zone.
Suppose you have a square shelter defined as hidden zone and an entry zone on the side of the shelter where the animal can enter it (see the figure below, left). When the animal enters the entry zone, one or more body points are tracked in that zone (1). As soon as a body point is not detected anymore (2), that body point is assumed to have entered the hidden zone and this body point is positioned in the center of the hidden zone during the time the animal is inside the shelter.
By default, the animal is considered to have left the shelter when it is next detected, that is, when its body points are “not missing”. However, every time an animal pokes its nose out, this may be recorded as an exit (middle, 2). Subsequently, retracting back into the shelter - without ever really leaving the shelter - would count as entering again. This results in an overestimation of how often the animal enters/exits the hidden zone. Therefore, EthoVision XT versions 5.1 and up have the possibility to also use the entry zone as leaving zone. The animal is then considered to have left the hidden zone when it was first considered to be in a hidden zone, and subsequently detected outside of the entry zone (see Right, 2).
In other words: the exit is counted only when the body point crosses the border between the entry zone and the rest of the arena. We recommend you use this function if you want to prevent an overestimation of entrances into, and exits from the hidden zone.
Left: If the animal's center point is first detected in the entry zone, and then disappears (because the apparent size of the animal becomes smaller than the minimum size set in Detection Settings, then the animal is considered to be in the shelter.
Right: The detection for exiting the hidden zone differs for not using or using the entry zone as a leaving zone also, respectively. (A) The subject is detected as having left the hidden zone as soon as the minimum subject size is detected anywhere within the arena. Depending on the minimum size set, only poking out the nose could count as "exiting". (B) The subject is detected outside the hidden zone, but will only be recognized as "out of the hidden zone" as soon as it crosses the border of the entry zone into the rest of the arena.
1.At the bottom of the Arenas and Zones section, click the Add Hidden Zone Group button.
2.Create a zone covering the area you want to define as a hidden zone.
If the Auto-label zones option is switched on, the zone is automatically named Hidden Zone 1. Right-click the name to rename it. If the auto-label option is switched off, click the Add Zone Label button on the toolbar, click the zone and rename the zone.
Note
▪If a hidden zone is included in a larger, overlapping zone, the time spent in the hidden zone is not included in the results for the larger zone. See a note under the topic In zone.
See also