The preference of a whale cannot be determined, but the physical and chemical changes caused by rainfall have measurable effects on their daily lives. These changes primarily involve acoustic interference and shifts in ocean chemistry, which influence communication, navigation, and food sources. Understanding the functional impact of rain on these large marine mammals provides insight into their adaptability within a constantly changing ocean soundscape and ecosystem.
How Rain Affects a Whale’s Senses
The most immediate impact of rainfall is the disruption of the underwater soundscape. The drumming of raindrops on the ocean surface creates a loud noise profile that dominates the natural acoustic environment. This surface agitation generates sound in the 1 to 50 kilohertz frequency range, a spectrum used by many cetaceans for communication and navigation.
For toothed whales, this noise interferes with echolocation, which they rely on to locate prey and navigate. Baleen whales, which use low-frequency calls for long-distance communication, also experience masking of their vocal signals. Studies using passive acoustic monitoring show that species like blue whales and fin whales alter their vocalization patterns in response to heavy rainfall events. This change is a functional response to increased ambient noise, shrinking their communication range and affecting their ability to coordinate activities.
The Effect of Freshwater Runoff on Ocean Chemistry
Heavy or prolonged rainfall leads to increased freshwater runoff from land into coastal waters and estuaries. This influx significantly alters the ocean’s chemical composition and physical structure. The lighter, less-saline water floats on the denser seawater, creating a distinct layer that causes thermal and salinity stratification.
Runoff carries nutrients, trace elements, and sediments, which fuel massive blooms of phytoplankton, the base of the marine food web. However, this terrestrial runoff also introduces pollutants. The subsequent decomposition of these algal blooms can severely deplete oxygen levels, creating low-oxygen areas known as dead zones. These dead zones displace or kill the fish and zooplankton that whales feed upon, indirectly affecting the whales’ foraging grounds and movement patterns.
Scientific Limitations in Determining Preference
Determining a whale’s emotional preference for rain remains beyond the current scope of marine science. Preference requires interpreting an internal, emotional state, so researchers cannot definitively say if a whale “likes” or “dislikes” the rain. Any observed behavioral change, such as diving deeper or shifting vocalizations, is recorded as a functional response to a physical stimulus.
Observing whales during heavy weather is logistically challenging, as boat-based surveys are often unsafe, limiting visual data collection. While passive acoustic monitoring can record their sounds, a lack of vocalization during a storm does not clarify if the whale has left the area, stopped calling, or is simply being masked by the rain noise. Scientists focus on the measurable impacts of rain—acoustic interference and ecosystem changes—treating the whale’s reaction as a physiological and behavioral adjustment.