Alarm Calling

The question of whether alarm calling is selfish or altruistic is a question that animal behaviorists have struggled with (Case, 2004). Although alarm calling may alert the rest of a group to predators so they can take action to protect themselves, an opposite argument can be made that alarm calling makes other animals more susceptible to predation by causing confusion or panic and thus making them more conspicuous to the predator than the caller is (Case, 2004). However, two factors can be used to determine if alarm calling is altruistic or selfish. The first factor is whether the alarm call may signal kin and thus acts as kin selection. The second factor is whether it can be proven that the caller puts themselves in danger to warn others (Case, 2004). There is conflicting evidence among prairie dogs that alarm calls are altruistic.

Photography courtesy of Roberta Stacy

In black- tailed prairie dogs, studies have shown that alarm calls not only warn offspring, but also warn nondescendent kin such as nieces, nephews and cousins (Hoogland, 1995). The evidence that these calls exist to warn nondescendent kin was that prairie dogs with no offspring in the territory called as often as those with offspring. In addition, Hoogland found that prairie dogs with kin within a close distance called more often than prairie dogs of the same sex that did not have kin nearby (1995). This seems to suggest that the alarm call is a form of kin selection.

It is more difficult to determine whether a prairie dog infact does put themselves in danger of predation while calling, however. Hoogland says that because alarm calls make the caller more apparent to the predator, the caller does make themselves more susceptible to predation (1995). However, there are two factors that act to decrease this danger. Hoogland says that the first is that it is difficult to determine which prairie dog is giving the call because of the “ventriloquial” nature of the call (p.172). In addition, there are selfish herd effects in the prairie dog colony that act to decrease the ability of a predator to assign a call to a specific animal (Hoogland, 1995). Often, after the call is sounded, other prairie dogs within the coterie do not automatically enter their burrows. Instead, they stand ontop of the mounds to try and spot the predator. Thus, the predator may now be able to see them as well (Hoogland, 1995).

There is some conflicting evidence as to which prairie dog usually sounds the alarm. In Black- tailed coteries, Hoogland stated that it is most often the closest prairie dog to the predator that calls the most (1995). However, in a similar study done on Gunnison’s prairie dogs, it was found that the prairie dogs that were located closest to the predator were less likely to give a call that a prairie dog farther away (Hoogland, 1996). These prairie dogs closest to danger often went into their burrow without calling (Hoogand, 1996). From this, Hoogland inferred that a prairie dog is put in danger when calling. There were not enough instances of predation in Hoogland’s studies to in fact conclude that the callers were more vulnerable to predation (Hoogland, 1996).

Cooperative Breeding
John Hoogland strongly supports the idea of cooperative breeding in prairie dogs (Hoogland, 1983). There has been some criticism of Hoogland’s belief of cooperative breeding in prairie dogs, especially by researchers Gail R. Michener and Jan O. Murie (1983). Nonetheless, Hoogland still insists that prairie dogs are cooperative breeders, although they may be much more competitive than other cooperatively breeding insects and birds (Hoogland, 1983).

Michener and Murie argue that prairie dogs only exhibit one of the benefits that helpers give to breeders (1983). This benefit is territorial defense. Territorial defense, they argue, however, is a benefit that can be selfish so Hoogland does not have enough evidence that this is a helping behavior (Michener & Murie, 1983). Hoogland, in opposition, states that black- tailed prairie dogs may exhibit all four benefits that come along with cooperative breeding (1983). Two of these behaviors prairie dogs definitely show, according to Hoogland. These are the active defense of young against predators and conspecifics by nonbreeders, and the grooming of offspring by nonbreeders. The other two cooperative behaviors that may be shown by black- tailed prairie dogs are defense of young by nonbreeders while mothers and offspring are underground and the feeding of the offspring by nonparents. This feeding may occur through communal nursing. Communal nursing may occur after offspring emerge from the burrow for the first time (Hoogland, 1995). During the time that the offspring emerge, some offspring may go into a nursery burrow for the night with another mother who is not there own. Because nursing happens at night, it may be inferred that the mother may nurse offspring that are not her own (Hoogland, 1995). This last behavior of communal nursing that Hoogland designates as a helping behavior does not follow the traditional definition of a helping behavior, however (Case, 2004). This is because the traditional definition of cooperative breeding helping behaviors include the behaviors that non- breeders exhibit towards nondescents, sacrificing their own reproductive success (Case, 2004). Communal nursing probably occurs when mothers mistake others offspring as their own, thus they are not giving up their own right to reproduce to nurse and they are not traditional helpers that do not have offspring at the time (Case, 2004; Hoogland, 1995).

Murie and Michener also found it hard to believe that helping behavior did exist between black- tailed prairie dogs because as coterie size increased, there was a decrease in the reproductive success of the breeders (1983). As Hoogland also originally, thought, it seemed that as the coterie size increased, so would the number of helpers (1983). However, as Hoogland stated in response to Murie and Michener’s criticisms, that as coterie size increases, so does the competition for resources. Hoogland argues that competition can exist in cooperatively breeding groups (1983).

Another issue that seems to be perplexing is that if intracoterie interactions are mainly hostile between females during the late breeding season and lactation, it seems impossible for helping behavior to exist (Murie and Michener 1983). This hostile behavior is greater during this time period between members of the same coterie than members of different coteries. However, Hoogland answers this by saying that although there is a greater number of hostile interactions between coterie members than noncoterie members at this time (probably mother- mother interactions), there is also a greater number of amicable interactions within the coterie (probably mother- nonbreeder interactions) (1983).

Although some sort of helping behavior does exist, Hoogland (1995) states that nonbreeders perform helping tasks when there is no better alternative, they are "simply making the best of a bad deal" (pp. 219).

Photograph courtesy of Roberta Stacy

Photograph courtesy of Roberta Stacy