how to make a Hibernation plot in r using ggplot2

Earlier today I helped make a figure for a proposal about marmot hibernation patterns. The goal was to make a figure similar to Figure 1 in Lee et al. 2016 (J. Mamm.), which shows the body temperatures of four marmots as well as the temperature of the soil in their burrow:

I was working with a 3-column dataset in tab-delimited (.txt) format that looked like this:

Date.Time    Temp    Label
5-9-2008 14:04    -3.67    soil
5-9-2008 14:44    -3.64    soil
5-9-2008 15:24    -3.61    soil
...
5-2-2009 14:36    37.23    marmot
5-2-2009 14:56    37.23    marmot
5-2-2009 15:16    36.12    marmot

The following code is my attempt to replicate the figure above using ggplot2 in R:

#load the ggplot2 library
library(ggplot2)

#import the data file
Data <- read.delim("~/Desktop/Marmots_and_Soil_Data.txt")

#define the format of our Date.Time column
Data$Date.Time<-strptime(Data$Date.Time, format= "%m-%d-%Y %H:%M")

#convert the Date.Time column to a format that ggplot2 can read
Data$Date.Time<-as.POSIXct(Data$Date.Time)

#plot the data
ggplot(data=Data, aes(x=Date.Time, y=Temp, group=Label, colour=Label)) + 
  geom_line(size=1) + 
  ylab("Temperature (ºC)") + 
  xlab("Date")