PATTERNS IN THE BEHAVIOR PHENOMENA

Most unusual animal behavior reported before earthquakes is not totally abnormal for the animals' repertoire but has been observed in the species under other circumstances (Table 1). The behavior sometimes resembles startle movements in response to a sudden stimulus; in other cases it resembles the orientation movements that animals use to investigate or avoid a stimulus. The behavior reported in postearthquake interviews resembles fear or escape reactions and ranges from mild response to bizarre behavior [Lott et al., 1980]. Investigators familiar with the full range of behavior for a species will often recognize that reported 'abnormal' behavior is actually species-typical behavior which may be triggered by a variety of stimuli [Moore and Stuttard, 1979] not necessarily related to earthquakes. For example, behavior such as cats hiding and pigs biting their tails (Table 1) also appears at times of stress unrelated to geophysical changes.

Much of the behavior resembles that reported for animals before geophysical events other than earthquakes, such as thunderstorms [e.g., Edwards, 1968; Bufe and Nanewicz, 1976] or sudden volcanic eruptions. For instance, dogs sniffed and pawed at the earth 2-4 days prior to the eruption in 1955 of Mount Kilauea, Hawaii [Bolt et al., 1975]. Cows abandoned their pastures 2 weeks before Volcan Arenal, Costa Rica, erupted in 1968 [Anderson, 1973], and dogs barked incessantly for minutes to hours prior to the 1965 eruption at Tall, Philippines [Anderson, 1973].

For a few major earthquakes, reports of unusual animal behavior have been widespread enough that it was possible to study the timing of the behavior (Tables 2a and 2b). For the Tangshan earthquake (M = 7.8, July 28, 1976), reports of fish, rodents, and wolves were cited as early as a month or two before the event [Academia Sinica, 1977b; Shen, 1978]. In the epicentral area of Tangshan, over 70% of the reported incidents took place within 1 day before the earthquake. Most incidents (70%) also occurred in areas which were to experience the greatest Mercalli intensities. Although in other earthquakes, unusual behavior of cows and horses has been noticed in the seconds or minutes prior to the shock [Lee et al., 1976; Tributsch, 1978], at Tangshan only 10% of the reported incidents for horses, donkeys, and cows occurred immediately before the earthquake. At Tangshan there were reports of earthquake lightning and changes in telluric currents the days before the earthquake (Academia Sinica, 1977b), but there were no reported foreshocks.

 

TABLE 2a. Temporal Distribution of Animal Behavior (as Percentage) Prior to Earthquakes:

Haicheng, China, Earthquake (M = 7.3), February 4, 1975, 19:36 Local Time

 

Dec.

Jan.

Feb. 1-2

Feb. 3

Feb. 4

Total n

Chicken

0

6

12

19

63

121

Cow and horse

10

0

0

28

61

174

Dog

0

13

0

33

54

74

Fish

24

17

8

18

33

61

Mouse and rat

6

27

4

21

42

243

Pig

0

5

28

14

53

359

Snake

16

71

8

2

3

23

Data are from Academia Sinica [1977a]. Total n is the total number of observations.

 

As early as a month prior to the Haicheng, China, earthquake (M = 7.3, February 4, 1975). [Academia Sinica, 1977a; Raleigh et al., 1977], unusual behavior in fish, rodents, and snakes was observed (Table 2). However, most of the unusual behavior took place within 2 days of the main shock. Numerous foreshocks and obvious groundwater changes also occurred 1 or 2 days before this event [Raleigh et al., 1977].

Rikitake [1978a, b] considered the temporal relationship between geophysical and behavioral precursors for the lzu, Japan, earthquake (M = 7.0, January 14, 1978). Nearly all physical precursors measured for this and other earthquakes occurred at least 2 days prior to the main shock, while most of the 129 behavior incidents happened within 24 hours of the earthquake. In Rikitake's [1978b] analysis most behavioral precursors coincided with a swarm of foreshocks a few hours prior to the main shock.

 

TABLE 2b. Temporal Distribution of Animal Behavior (as Percentage) Prior to Earthquakes:

Tangshan, China, Earthquake (M - 7.8), July 28, 1976, 03:30 Local Time

 

Before July 26

July 26

July 27

July 28

Total n

Bird

12

16

58

12

24

Cat

29

14

46

11

28

Chicken

21

18

57

4

128

Cow and horse

0

4

86

10

52

Dog

16

2

61

20

44

Fish

50

0

41

9

23

Goat and sheep

25

3

64

6

31

Mouse and rat

54

18

26

2

165

Pig

42

6

39

11

57

Data are from Academia Sinica [1977b]. Total n is the total number of observations.

 

The great variability of animal behavior before earthquakes is apparent from postearthquake interviews such as the standardized studies of Lott et al. [1979a, b]. Unusual barking of dogs was noted by observers prior to one earthquake in Turkey but was absent before an earlier earthquake in the same area [Toksöz, 1977]. Individual animals of the same species, even when located in the epicentral area, did not respond in the same way before the 1977 Willits, California, earthquake (M = 4.7) [Lott et al., 1979a].

This variability has two sources: behavioral differences among individual animals, even within the same species, and geophysical differences between earthquakes. An important factor is the difference in response thresholds and differential tendencies to react between different animals. In addition, it is clear from comparative studies [Lott et at., 1980] that unusual behavior is observed before some earthquakes but not others. The same type of interview study was conducted after four recent California area earthquakes: Willits, November 22, 1977 (M = 4.7); Landers, March 15, 1979 (M  = 5.5); Coyote Lake, August 6, 1979 (M = 5.4); and Mexicali, October 19, 1979 (M = 6.9). All four had strike-slip faults with rather shallow epicenters located in rural areas. Only the Willits earthquake had a significant number of behavior precursors [Lott et al., 1980].

From an examination of the available data for 36 earthquakes on four continents (Figure 1) a few generalizations about the reported unusual animal behavior are possible.

1. Most, but not all, of the animal behavior precursors occur close to the epicenter within 1 or 2 days of the earthquake. The species primarily reported are domestic mammals, such as dogs, probably because of their close association with humans, and animals of commercial importance, such as horses and chickens.

2. Some, but not all, of the behavior precursors occur within 'a few minutes' before the earthquake [Lawson, 1908; Penick, 1976; Tributsch, 1978]. For these precursors it is difficult to dismiss the hypothesis that the animals are sensing the vibrations of the P arrival from the earthquake, while humans sense only the later and stronger S or surface waves. For example, Kilian [1964] found that horses and pheasants responded about 5-10s before humans felt the earthquake in an aftershock sequence in Chile. It is possible that not all of these behavioral precursors are caused by the arrival of the P wave, as other physical changes could be occurring simultaneously. However, in recent careful studies [Rikitake, 1976; Lott et al., 1979a, b], phenomena that may coincide with the P arrival are placed in a separate category from earlier behavioral precursors.

3. A few of the behavior precursors actually are reported days to weeks before the earthquake, and some of these occur at a considerable distance from the epicenter. The species most often mentioned in these reports are fish [Terada, 1932; Rikitake, 1976] and rodents [Academia Sinica, 1977b].

Fig. 1. Distribution of animal behavior incidents according to the distance from the epicenter and the time before the main shock of 36 different earthquakes in Europe, Asia, North America, and South America. Symbols indicate reports on the following animals: catfish, eels, other fish, frogs, snakes, turtles, sea birds, chickens, other birds, dogs, cats, deer, horses, cows, rats, and mice. Data are nonsystematic and collected from many sources [Kilian, 1964; von Hentig, 1923; Simon, 1975: Lee et al., 1976; Academia Sinica. 1977a, b; Shaw, 1977; Rikitake, 1978a, b, Tributsch, 1978].