2012 COURSE DATES: AUGUST 4 – 17, 2012 - Sirenian International

MA”: BEHAVIORAL SAMPLING METHODS 115
was 3.2%. Several methodologists (e,g., Tyler 1979) have demonstrated the
validity of PAS and point sampling using statistical models, but no one has
contrasted these methods using actual observational data.
Incident sampling-Alternate names: all-event sampling, all-occurence sam-
pling, all-animals sampling. Incident sampling entails scoring all behavioral
events of a specific type in a group. This method is not applicable for most
behavioral states. The observability of the events is key to the success of this
method. The behaviors themselves must be obvious enough to alert the ob-
server (e.g., breaching). In addition, the observer must be able to record all
the events regardless of how many animals are present. Thus, for incident
sampling to be successful, the behavior must be sufficiently infrequent to allow
complete recording for the group. As Altmann points out, this is a form of
continuous sampling (referred to as focal animal sampling in her paper) of a
group for a restricted set of behaviors. However, with continuous sampling,
the individual animals are identified. During incident sampling, distinctions
between subjects may or may not be made. Observers should still make every
effort to determine whether the same or different animals are exhibiting the
behavior(s). Two areas can be problematic. First, animals may tend to repeat
displays, thus becoming overrepresented in the dataset. Second, if group com-
position changes often (Table 1) it may be difficult to calculate event rate as
a function of group size or structure.
In the survey, 16% of the studies used incident sampling. Studies that
identified their method as “focal-group-sampling” were sometimes coded as
using incident sampling if they scored a very restricted set of obvious behav-
iors. For example, breaches and lobtails are so visible that observers are likely
to detect each occurrence within a group. Similarly, if observers could deter-
mine how many animals were within acoustic range, then incident sampling
could apply to studies of vocalizations.
Incident or all-event sampling is valuable for cetacean researchers who wish
to focus on specific dramatic or easily recognized events that involve few an-
imals. For example, observers could use this method to compare successful and
unsuccessful killer whale hunting attempts via beaching. Dramatic surface
percussive displays, such as breaching or lobtailing, can also be observed re-
liably in groups (Waters and Whitehead 1990). Incident sampling requires
that the observer systematically record every event. Incident sampling may be
adopted with a group protocol, but the observer should still be able to dis-
tinguish which animal (or agehex class member) is engaging in the behavior
to avoid misattributing the behavior pattern equally to all individuals.
Sequence sampling-In sequence sampling, the observer focuses on sequences
of behavior or on particular interactions, rather than individuals, and system-
atically records all relevant behaviors that occur during the event(s), main-
taining the sequences of behaviors in the record (Altmann 1974). Parameters
defining how an interaction begins and terminates must be specified in se-
quence sampling. For example, observers may score sequences of behaviors
among surface-active groups of humpback whales by defining the beginning
of the sequence as “male humpback whale challenges principal escort by ap-