Data from: The contrasting hidden consequences of parasitism: effects of a hematophagous nematode (Uncinaria sp.) in the development of a marine mammal swimming behavior.

1. Parasites are an important part of ecosystems, playing a critical role
in their equilibrium. However, the consequences of parasitism beyond the
direct effects associated with disease and mortality are not completely
understood. This gap in knowledge is in part due to the difficulties to
isolate the effect of single parasite species on physiological and
behavioral traits in natural systems. 2. The South American fur seal
(Arctocephalus australis)-hookworm (Uncinaria sp.) interaction offers an
ideal system to overcome these difficulties and study the behavioral and
physiological effects of parasites in their hosts. 3. Hookworms cause
stunted growth and anemia in pinniped pups, which could affect early life
active behaviors such as swimming. The aim of this study was to determine
the effects of hookworms (Uncinaria sp.). on the development of swimming
capabilities in A. australis through physiological and ethological
analyses. 4. Higher parasite burden was associated with reduced growth
rates and lower blood hemoglobin concentrations, whereas scaled body mass
and blood hemoglobin levels had an important positive effect on the water
activity of the pups. However, anti-hookworm treatment did not affect the
level of water activity of the pups, and pups with high hookworm burden
increased their time budget in water. This was probably related to lower
maternal attendance in heavily parasitized pups, leaving these pups more
time to perform water activities. Therefore, pups with heavy hookworm
burden, despite having decreased growth rates and blood hemoglobin
concentrations, compensated for their handicap in physiological traits
related to swimming by spending more time in the water. 5. This work
offers new insights to understand the contrasting effects of parasites on
aquatic organisms, and the compensatory mechanisms employed by infected
animals to avoid the worst consequences of parasitism.